Learn Python Programming - Python Course

In this course, you're going to learn everything you need to get started with Python just be aware that I have to design this course for developers so if you have very little or no programming experience check out my other Python course for beginners you can see the link on the top right corner of this video python is the world's fastest-growing and most popular programming language not just amongst software developers but also amongst mathematicians data analysts scientists accountants network engineers and even kids in fact it's the ideal programming language to learn first but what makes Python so special here are six reasons with Python you can solve complex problems in less time with fewer lines of code than many other languages that's why huge companies like Google Spotify Dropbox and Facebook have embraced this beautiful and powerful language here is an example let's say we want to extract the first three characters of the text hello world this is the code we would have to write in c-sharp this is how we would do this in JavaScript and here's how we would do it in Python see how clean and simple the language is and that's just the beginning Python is a multi-purpose language and you can use it for a wide range of jobs such as data analysis AI and machine learning writing automation scripts building web mobile and desktop applications as well as software testing or even hacking so if you want a high-paying long lasting career in any of these areas especially AI and machine learning Python is the language to put those opportunities at your fingertips in fact according to indeed.com the average salary of a Python developer in the US was over one hundred and fifteen thousand dollars in March 2018 and here are four more reasons that make Python the most desirable language Python is a high-level language so you don't have to worry about complex tasks such as memory management as you do in C++ it's cross platform which means we can build and run Python apps on Windows Mac and Linux it has a huge community so whenever you get stuck there is someone out there to help and it has a large ecosystem of libraries frameworks and tools whatever you want to do it is likely that someone else has done it before because python has been around for over 20 years there are two versions of Python out there Python 2 which is the legacy version of Python and is going to be supported until year 2020 and Python 3 which is Python for the future in this course you're gonna learn Python 3 hi my name is Muhammed Ani and I'm going to be your instructor in this course I'm a software engineer with 18 years of experience and I've taught way over a million people how to code or how to become top professional software engineers to learn more about me and my courses head over to code with mass comm alright now let's get started alright now we're ready to download and install Python the first thing I want you to do is to open up your browser and head over to python org on this page under the downloads you can see the latest version of python currently the latest version is 3.7 chances are in the future when you're watching this video there is a newer version available don't worry all the materials in this course will continue to apply with the future versions of Python so go ahead and download Python then run it if you're on Windows we're going to see this checkbox here add Python to path this is very important make sure to take it otherwise you're not going to be able to follow the course so now go ahead and install it now let's verify that we have installed Python properly if you're on Windows here in this search bar type CMD which is short for command prompt now here in command prompt type Python you can see we have successfully installed Python version 3.7 now to exit press ctrl-z and then enter if you're on Mac press command and space this opens up the spotlight search so here type terminal terminal and Mac is like command prompt on Windows now Mac and Linux why default come with an older version of Python that is version 2 so if you type Python you can see Python 2 here let's type what we want so press ctrl D to exit and then run Python 3 and this verifies that we have successfully installed Python 3.7 so this environment you see here is what we call Python interpreter here we have this interactive shell that is really useful for experimenting with some Python code so here we can write expressions like 2+2 or any kind of valid Python expressions this is similar to your JavaScript console in the browser so if you want to quickly experiment with something can simply do it here but to build real programs we need a code editor and that's what I'm going to talk about next to build Python programs you have two options you can use a code editor or an IDE which is short for integrated development environment an IDE is basically a code editor with some fancy features such as Auto completion debugging unit testing and so on for both editors and IDs there are lots of options out there the most popular editors are Visual Studio code or yes code atom and sublime you can use the editor that you prefer the most popular IDE is PyCharm which is a JetBrains product in this course I'm gonna use the S code because that's my favorite code editor and later I'm gonna show you how to install an extension to convert the s code into a powerful IDE for building Python programs so if you don't have V s code head over to code dot visual studio comm and download the latest version of V ESCO now it vs code open on the top go to the file menu and then open somewhere on your desk create a new folder let's call that folder hello world as usual now open this folder now here on the left side we have the Explorer panel where you will see all the files and folders in your project so let's add a new file here and call it app dot pi now you may see an error on the bottom right corner of the screen don't worry about that we're gonna fix that later in this section so close this now let's write a simple Python program once again I've designed this course for people with some programming experience so you should know your variables functions conditional statements like if else for loops while loops you should know the basics if you don't please look at my other Python course for beginners you can find a link on the top right corner of this screen so in Python we have a bunch of built-in functions one of them is print which we can use to print something on the terminal let's add a string here hello world but let's make it more fun by adding a happy Persian cat here now let me show you something cool let's add another print statement here we add a string like an asterisk in Python you can multiply a string by a number like 10 and this will repeat that string 10 times take a look so save the changes once again you may see this error popping up don't worry about it we'll fix that later now we need to go back to the terminal to run this program however we don't have to constantly switch back and forth between vs code and the terminal because here we have an integrated terminal you can open that by pressing ctrl and backtick that is the key before number one on your keyboard it's right below the escape button so here's our integrated terminal so if you're on Windows type Python if you're on Mac Python 3 and an app that PI and here's the output of our program next I'm gonna show you how to convert vs code into a powerful idea for building Python programs in this lecture I'm gonna show you how to convert vs code to a powerful IDE by using an extension called Python with this extension or plugin we get a number of features such as linting which basically means analyzing our code for potential errors you also get debugging which involves finding and fixing errors we'll look at this later in the course you also get auto completion which basically helps us write code faster so we don't have to type every character we get code formatting which is all about making our code clean and readable just like how we format our articles newspapers books to make them clean and readable we get unit testing which involves writing a bunch of tests for our code we can run these tests in an automated fashion to make sure our code is behaving correctly and finally we get code snippets which are reusable code blocks and we can quickly generate so we don't have to type them all by hand now don't worry about memorizing any of these as we go through the course you're going to learn about these features now here in vs code on the left side click this icon this opens the extensions tab so these are the extensions that we can install in vs code to bring in additional functionality here under the recommended tab you can see the python extension if you don't see this simply type Python here on the top and here's the extension to go ahead and install this and then you'll have to reload vs code now here on the bottom right corner you can see this message linter pilant is not in stock so as I told you before linting is about finding potential errors in our code linter is a program or a tool that analyzes our code and finds these potential problems now for Python there are several enters a fter pilant is one of the most popular ones that this Python extension uses by default so we need to go ahead and install pylons as well now to do this first we need to change our Python environment so if you look here on the bottom left corner you can see the current python that is used in vs code that is python 2 point 6 point 9 on my machine chances are you see a different version here so click here and in this list make sure to select python 3 point 7 so these changes our python environment to python 3 point 7 and then we can install pilant by clicking this button ok pilant is installed beautiful in the next lecture I will show you how linting works in this lecture I'm gonna show you linting and action so let's start by writing some invalid code like this print space with no parentheses and then hello work earlier I told you that print is a built-in function and whenever you want to use or call a function you should always use parentheses now to be more precise this is actually valid Python 2 code but because we're using Python 3 here this is invalid code from Python 3 point of view so now when I save the changes you can see this red underline here let's hover our mouse over this underline you can see this tooltip it's coming from Pyland and here's the error message missing parenthesis in call to print did you mean print with parentheses that this is the benefit of linting as you're writing code you can see potential problems in your code you don't have to wait to run your program to see these errors so now if we put parentheses here and save the changes you can see that red underline is gone let's look at another error let's type two plus and then save the changes earlier we run this code in Python interpreters interactive shell there we got a syntax or grammar error so if you hover your mouse here one more time you can see pylons is telling us that this is invalid syntax or invalid grammar it's like an incomplete sentence so this is linting in action now let me show you a couple useful shortcuts here on the top look at the View menu here we have these problems menu look at the shortcut on Mac is shift command and M on Windows is probably shift control M so as you're working with vs code try to memorize these shortcuts because they really help you write code faster now let's take a look at these problems panel so this problems panel lists all the issues in your code in one place so if you have an application with multiple files this is really useful because some of those files may not currently be open so this linter Pyland will analyze all your files and if it finds any issues it will list them here in the problems panel now you can also put this on the right side of your screen so let's put it here so as you write code these problems will appear here now let's fix this issue so I'm gonna add three here save the changes and you can see the problem disappear and one last thing before we finish this lecture once again on the top let's go to the View menu the first item is command palette this is a very important feature in vs code once again look at the shortcut that is shift command and P on Mac or shift control P on Windows this command palette you can execute various commands in vs Co if you type lint here you can see all commands related to linting as you can see all these commands are prefixed with Python because these commands come with a Python extension that we installed earlier so these are additional features available to us in vs code the first command here is select linter in this list you can see various linters available for pilot so as you're reading tutorials or talking to other people you will hear about linter such as flake ate my pie pep 8 and so on different developers prefer different linters I personally prefer pilant that is the most popular one and that's the default linter set and the Python extension of vs code if you're adventurous we can try using other linters on your own the difference between these linters is in how they find and report errors some error messages are more meaningful or more friendly the others are more ambiguous so that's all about linting in the next lecture we'll talk about formatting code in Python community we have a bunch of documents called Python enhancement proposals or peps here on Google if you search for Python peps you can see the list of all these paps under python.org slash dev slash paps let's have a quick look here so here are the paps you can see each PAP has a number and a title the one that is very popular amongst Python developers is pep 8 which is a style guide for Python code a style guide is basically a document that defines a bunch of rules for formatting and styling our code if you follow these conventions the code that you write will end up being consistent with other people's code now if you have time you can go ahead and read this PAP 8 documentation but if not don't worry because throughout this course I'm gonna explain the key things in pep 8 in this lecture I'm gonna show you a tool that helps you automatically format your code according to pap 8 so back in vs code let's write some Python code x equals one here I'm declaring a variable and setting it to one if you're not familiar with variables don't worry in the next section you're going to learn about that so according to peb 8 this code is considered ugly because by convention we should add a space around this equal sign or the assignment operator now since you're starting out with Python you probably don't know these rules so let me show you a tool that helps you automatically format your code let's revert this back to its original state now we need to go back to the command palette remember so it's right here under view and the shortcut is shift command and P here if you search for format you can see this command format document the first time you execute this command you're going to see this message here formatter Auto kept 8 is not installed so there are a bunch of tools for formatting Python code the most popular one is Auto kept 8 and this is the tool that this Python extension we installed uses to format our code so let's go ahead and install this good now one more time let's open up the command palette and execute format document see is tool automatically formats our code beautiful let's take a look at another example I'm going to declare another variable Y and set it to 2 and a variable with a long name like unit underlined price I'm set this to 3 now some developers have this habit of formatting their variable declarations like this so they put all these equal signs in the same column according to pep 8 this is considered ugly so once again let's format our code that is better beautiful now let me show you a trick opening up this command palette and searching for format document every time is a little bit time-consuming so I want to show you how to have your file automatically formatted as soon as you save the changes on the top let's go to the code menu preferences and settings here in the search box search for format on save so we have this option editor format on save take this now back to apt at PI I'm gonna change the formatting of these lines make them really ugly now as soon as I save the changes you can see my code is reformatted beautiful so you have learned that in order to run this Python program we'll have to open up the terminal window and run Python on windows or Python 3 on Mac and an app that pi this is a little bit tedious so let me show you a shortcut once again let's go to the extensions panel here search for code runner there are multiple code runners out there the one that I'm talking about is this one with the yellow icon so go ahead and install this and then reload vs code now instead of opening up the terminal and manually typing python after pi all you have to do is to press ctrl alt and in you can see the output here beautiful just be aware that if you make any changes you'll have to save the changes before using this shortcut otherwise you're going to see the old result now there is a tiny problem here so you can see this is the command that is executed to run this Python program so by default this command is using Python - U and here is the name of our file if you're on Windows that's perfectly fine but if you're on Mac you know that Python refers to Python - here we want to change this to Python 3 this is very easy once again on the top under the code menu let's go to preferences settings and then here under this dot-dot-dot go to open settings that JSON now here in the search bar type code - runner dot executors map so these are the default settings used by this code runner extension you can see this extension support executing code in a lot of languages like JavaScript Java and so on now if you scroll down here you can see Python and in front of that you can see the command that is used to execute Python code we need to change this however we cannot change the default settings we should change the user settings so on the right side after the last setting type a comma and then in quotes type code - runner dot executors map and then press enter this will automatically copy all the settings on the left side to the right side now we can easily change one of this so here's Python let's change the command to Python 3 you only have to do this if you're on Mac and by the way sorry if we have mentioned Windows and Mac a few times throughout this course that's pretty much it we are not going to differentiate between Windows and Mac in the future so save the changes and we're done when we talk about Python we mean two separate things that are closely related python language and a particular implementation python as a language is just a specification that defines a set of rules and grammar for writing Python code a Python implementation is basically a program that understands those rules and can execute Python code earlier in the course we downloaded Python from python.org this is the default implementation of Python called C Python it's a program written in C that's why it's called C Python so here in terminal when we run Python we get this C Python this is the default implementation of Python there are a few other implementations out there such as JSON written in Java ironpython written in c-sharp and pi pi written in a subset of Python itself as new features are added to the Python language they are first supported by C Python because that's the default implementation and then they will gradually come to the other implementations in theory if we give some Python code to any of these implementations we should get the same result but in practice that's not always the case certain features may be available in one implementation but not another or they may just behave a little bit differently in a particular implementation now you might ask what is the point of this why do we have several implementations of Python wouldn't see Python be enough well it's for the same reason that we have multiple operating systems or multiple browsers or multiple programming languages after all these years B programmers haven't agreed on a single programming language and that's the same story with Python implementations however there is one technical reason behind these implementations that you should be aware of since JSON is implemented in Java it allows you to reuse some existing Java code in a Python program so if you're a Java developer and you want to import some Java code into a Python program you should use JSON instead of C Python similarly I Python is written in c-sharp so if you're a c-sharp developer and want to bring some c-sharp code into a Python program you will have to use ironpython next we'll look at how exactly C Python execute Python code the programming languages we use like C C sharp Java Python these are all simple text-based languages that we humans understand computers don't understand them they only understand machine code so if we have some code written in C we should convert it to machine code and that's the job of a C compiler so a C compiler is a program that knows how to convert or compile C code into machine code however this machine code is specific to the type of CPU of a computer so if we compile a C program on a Windows machine we can't execute it on a Mac because Windows and Mac have different machine code just like how people from different countries speak different languages Java came to solve this problem Java compiler doesn't compile Java code into machine code instead it compiles it into a portable language called Java bytecode which is not specific to a hardware platform like Windows or Mac now we still need to convert Java bytecode to machine code so Java also comes with a program called Java Virtual Machine or JVM for doing this when we run a Java program JVM kicks in it loads our Java bytecode and then at runtime it will convert each instruction to machine code with this model we can run Java bytecode on any platforms that have a JVM we have JVM implementations for Windows Mac and so on so the JVM implementation on Windows knows how to convert Java byte code into machine code that a Windows machine can understand c-sharp and Python have also taken the same route so there are platform-independent when we run a Python program using C Python first it will compile our Python code into Python bytecode then it will pass that bytecode to Python virtual machine which will in turn convert it into machine code and execute it this is how C Python works in the last lecture we talked about various Python implementation I told you that if you want to reuse some java code in a Python program you should use Java now let's see how JSON makes this possible when you use JSON to run a Python program instead of compiling your Python code into Python bytecode it will compile it to Java code so we can take this Java bytecode and run it using java virtual machine and that's why you can import some java code into a Python program when using jython because the end result is Java bytecode which will eventually be executed by Java Virtual Machine so that brings us to the end of the first section if you have enjoyed this course so far please like this video and share it with others in the next section you're going to learn Python Basics in only one hour I hope you enjoyed this section and thank you for watching well hello Marsh here thank you for watching my Python tutorial I wanted to let you know that this tutorial is the first two hours of my complete Python course where you will learn how to use Python in real-world scenarios such as data analysis and visualization automating repetitive boring tasks that involve working with files and folders spreadsheets PDFs data compression sending emails web crawling consuming API is like Yelp to get information about businesses and much much more this course comes with a 30 day no questions asked money back guarantee and a certificate of completion if you're interested click the link below this video to access the course all right let's start this section by a discussion of variables and the built-in primitive types in Python including integers floats boolean's and strings so here I'm gonna define a few variables starting with the first one students count note that here all the letters are lowercase and we're using an underscore to separate multiple words this is the naming convention we use in Python so here we said students count to let's say a thousand this is an example of an integer let's look at an example of a float so we said rating two for let's say 99 here's another variable is published we set this to true or false note that the first letter is uppercase and finally let's take a look at an example of a string so we set course name to Python now in Python you can use either double quotes or single quotes or you can use triple quotes if your string is multiple lines for example here I can put triple quotes and in between them I can add a string that has multiple lights okay now one interesting feature in Python is that you can initialize multiple variables on the same line for example let's say we have coordinates like x and y we can initialize these two on the same line so we can set X comma Y we set it to 1 comma 2 this line is exactly equivalent to these two lines so it's a shortcut and finally just like almost every programming language we can set multiple variables to the same value for example we can set x and y to 1 so these are the basics of variables next I'll talk about the dynamic nature of Python in terms of typing programming languages fall into two categories static languages like C++ C sharp and Java and dynamic languages like JavaScript Ruby and Python in static languages when declaring a variable we need to specify its type for example in c-sharp when declaring this variable we need to set its type to an integer so with this the type of this variable will always be an integer when we compile this program or compiler knows that students count is an integer so if you accidentally try to set it to let's say a boolean later on the compiler will complain this is how static languages work in dynamic languages like JavaScript and Python we don't have this behavior so we don't set a type when defining a variable we just define a variable by setting it to a value so in dynamic languages the type of a variable is determined at runtime now here if you hover your mouse over students count you can see this is an integer so when working on a large complex program if you want to know the type of a variable you can simply hover your mouse over it we also have this built-in function called type we can pass a variable or an object to it like students count and then print this on the console so let's run this program you can see the type of students count is a class of integer what is this Python is an object-oriented language so here we have the concept of classes if you're not familiar with classes don't worry I'm gonna talk about them in detail later in the course all I want you to know now is that in Python we have a class called int that represents integers so all integers are instances of this class let's take a look at a few more examples so here in this interactive shell let's look at the type of a float once again it's a class called float let's look at type of a boolean this is also a class called bool and finally let's look at type I'm a string that's a class called stir so here's the take away Python is a dynamic language which means the type of variables are determined at run time as opposed to compile time sorry the last lecture you learned that Python is a dynamic language which means the type of variables is determined at run time so here we have this variable age set to an integer now we can reset this to a string this is perfectly valid Python code so if we print a age and run this program you can see our program is running successfully now if you come to python from a static language like C sharp or Java you probably don't like this but the good news is that in Python 3.6 we have a new feature called type annotation or type hinting so we can annotate our variables with their type so we had a colon here and then int for integer now when I save the changes everything is still valid if I run the program there are no errors because python is a dynamic language however there is a new lantern called my PI that checks for these type annotations so if you define a variable as an integer and then set it to a string my pie is gonna complain let me show you so open up the command palette and type select linter correctly you can see we are using pi lint in this list select my pi now the first time you do this you're gonna see a message on the bottom right corner of the screen telling you that my pine is not installed so go ahead and install that now on line two you can see a red line under H let's have a look here so my pi is giving us an error incompatible types in assignment so this is all about type annotation or type in ting so here we have this variable X set to 1 when we run this program Python interpreter will allocate some memory to store this number 1 so our X variable is purely a label for that memory location let me show you so here we have this built-in function called ID we can pass the variable here like X and this will return the address of the memory location that X references so now let's print this on the console there you go so this is the address of the memory location where we have stored number one now one thing you need to know about the built-in primitive types that I've talked about so far like numbers strings and boolean is that all these types are immutable which means their value cannot change so here if we try to update X python interpreter is going to allocate some new memory to store the updated value in other words what we have at this original memory location will not be affected because integers are immutable let me show you this so here after we print the idea of X I'm gonna increment X and print its ID one more time see what we get we get two different addresses so our X variable or X label was originally referencing this memory location at this memory location we have the number one because integers are immutable we cannot change the value at this memory location so on line four when we update X python interpreter will allocate some new memory at this location and then X will reference this new memory location now because we don't have a reference to the original memory at some point Python garbage collector will automatically release this memory so this is how immutable types work now let's see what would happen if X was set to a mutable type here is an example so in Python we have a concept called lists for storing a list of objects so here we use square brackets to indicate that this is a list we can add multiple objects here now on line four let's add a new number to this list so we call X dot append and pass four here now let's run the program one more time so as we can see the address is not changed because lists are mutable so whenever we change them by adding new objects to them or removing existing ones the changes are applied at the same memory location so this is the difference between mutable and immutable types over the next few lectures we're going to take a closer look at strings so here we have a variable of type string to get the number of characters in this string we use the built-in Len function now look at the intellisense this function returns the number of items in a container so it's not specific to strings it's a generic reusable function we can pass the a string here and this will return the number of characters in the string or we can pass a list and this will return the number of items in the list so here let's pass this course variable and print the length so we have 18 characters beautiful similar to many other languages we can access individual characters using square bracket notation so to get the first character we use square brackets 0 because the index of the first character here is 0 now let's print this run the program so we get P now one interesting feature in Python that I personally haven't seen in other programming languages is a negative index so here let's duplicate this line and pass negative 1 what do you think we're gonna get well if 0 represents the first character negative 1 takes us back to the end of the string so it returns the first character from the end of the string let's run this program so we get G similarly we could pass negative 2 and this will return the second character from the end very powerful now using a similar syntax we can also slice strings so let's duplicate this line to slice the string we need to pass two indexes the start index colon the end index so this will return all the characters starting from the start index all the way up to the end index but it doesn't include the character at the end index in this example it's going to return zero one and two these three characters but not the character at index 3 ok so let's run the program we get the first three characters beautiful now we can exclude either or both these indexes and Python will assume default values so let's duplicate this line and exclude the start index what do you think python is going to put here it's common sense it's going to pass zero as the start index so let's run the program you can see we get the same result so these last two expressions are exactly the same now what if we exclude the end index what do you think Python is going to put here it's going to pass the length of the string so let's run the program you can see this returns the entire string and finally if we exclude both the start and end index again we get the same result so let's verify this beautiful now one thing you need to take into account here is that whenever we access an individual character or a range of characters Python interpreter is going to allocate some new memory and copied those characters into that new memory location because as I told you before strings are immutable so the value that we have at the original memory location that is Python programming will not be affected we can verify this so let's print ID of course and then print ID of course of zero and then run the program you can see two different addresses here that is because strings and other primitive types like numbers and billions are immutable in Python here we have this message variable set to this string Python programming now let's say we want to display a double quote right here the problem we have is that this second double quote indicates the end of the string so python interpreter will not be able to run this code now there are two ways to solve this problem one way is to replace these double quotes at the beginning and end of our string with single quotes so single code here and one more here if we run this program we see this double code just before programming beautiful but let's say for whatever reason you want to use double quotes here perhaps to be consistent with the rest of our code so how can we display another double quote in the middle of this string well in Python we have a concept that is borrowed from the C language that is called escape character so in Python strings backslash has a special meaning and we refer to it as an escape character so Python interpreter sees this backslash as a special character it has a special meaning and depending on the character that comes after that it will interpret it differently let's see this in action so now when we run this program we can see our double code here but the backslash character is not there because backslash is an escape character so in this case it's used to escape the double code now we refer to these two characters as an escape sequence in Python we have a few other escape sequences that you should be aware of let me show you so this hash sign is an indication of a comment line so it's not executed you have seen backslash double quote we also have backslash single code for displaying a single quote in our string we also have double backslashes so if you really want to have a backslash in your string you should prefix it with another backslash here is an example let's run this program and here's our backslash and finally the last escape sequence is backslash n which is short for new light so here if I add a backslash N and run this program you can see programming is on the second line now this is OK for a simple string like Python programming here but if you're trying to format a complex string into multiple lines it's better to use triple quotes otherwise you'll end up with a lot of pack /n sequences and that looks pretty ugly so here we can use triple quotes and simply add Python newline programming so when we run this program we get exactly the same result as before but not quite exactly because here we have one new line on the top that is because I put Python on a new line if I put Python right in front of double quotes run the program again that new line disappears so here are the escape sequences in Python here we have two variables first and last let's say we want to print my full name on the console so we can define another variable full set it to first then concatenate it with a space and one more time concatenate it with last now when we print full we get my full name on the console beautiful now this approach are using concatenation to build a string is okay but there is a better and newer approach we can use formatted strings so here we can set full to this string and prefix it with an F which can be lowercase or uppercase it's formatted string doesn't have a constant value like these two strings here it's actually an expression that will be evaluated at runtime so here we want to add our first name we use curly braces to print the value of the first variable after that we add a space and then we add curly braces one more time to print the last name so at runtime this expression will be evaluated what we have in between curly braces will be replaced at runtime now let's run this program one more time we get the exact same result just be aware that you can put any valid expressions in between curly braces so earlier you learned about the built-in Len function we can call Len here to get the length of this string let's run this program one more time so we get four we can also replace last with an expression like there's two plus two let's run this program we get four and four so when using formatted strings you can put any valid expressions in between curly braces and it's lecture we're going to explore a few useful methods of string objects in Python so this course variable we have here is a string object which means we can use the dot notation to find all the methods or functions applicable on strings here we have a large list of functions or more accurately methods in this lecture I'm gonna quickly show you a few of them you can learn about the rest on your own so here let's say we want to convert this course to uppercase we can use the upper method and print the result and we'll get this uppercase string here similar to that we have lower to convert it to lowercase we also have title which will convert this to title case which means the first character of every word will be uppercase and this is useful for blog posts product titles courses and so on so let's run this one more time we get this string here another useful method is strip for trimming whitespace so if we have a couple of extra whitespace at the beginning or end of this string we can get rid of them using the strip method and this is useful when you get input from the user so a print course that strip save the changes note that in the previous examples you can see those extra white spaces at the beginning but when we call the strip method those spaces are gone we also have left and right strip for removing the whitespace from the beginning or end of this string now if you want to find the index of a character or a substring in your string you can use the find method so let's print course that find let's search for pro run the program so the index of pro here is 9 now if I change this to lowercase P we'll get negative 1 because string comparisons are case sensitive and we don't have these exact three characters in our course variable now if you want to replace a character or a sequence of characters you can use the replace method so let's print course that replace let's replace all capital pees ways a hyphen and with this we'll get this weird string here and finally to check for the existence of a character or a sequence of characters in your string you can use the in operator so let's see if we have programming in this course object let's run the program and we get false because I realize that I missed the letter R here so let's run the program one more time this time we get true now we also have the not operator so you can prefix this with not and this time we'll get false so we have covered strings now let's look at numbers we have a few different ways to represent numbers in Python we can use decimal numbers that you have seen before we can also represent them in binary format so we prefix the number with 0 B as in short for binary and then we'll add individual bits for example 0 B 10 which is the number 2 in binary system now let's print X we'll get 2 if you want to print the binary representation of this number you can use the built in bin function so bin takes any numbers and returns its binary representation there you go we can also represent numbers in hexadecimal format so we said X - 0 X as the prefix and then we'll add our hexadecimal number let's print X so we get 300 which is in the decimal system if you want to print this in the hexadecimal format you would use the built-in hex function let's run this program one more time and now we get 0 X 12 C beautiful in Python we also have support for complex numbers so complex numbers in maths take the form a plus B I if you're not familiar with this don't worry this is a concept used in mathematics so if you want to use Python to build web applications you're never gonna use this but very briefly let me show you how you can represent complex numbers in Python so here we can set X - 1 + 2 J so J in Python is like I or imaginary number in math you can use either lowercase or uppercase J whatever you prefer now let's print X we'll get this complex number here you in Python we have all the arithmetic operators that you have probably seen before for example we can set X to 10 plus 3 we have addition I have subtraction multiplication division but we actually have two kinds of division operators let's look at the first one so print X as you can see the result of this division operator is a floating-point number if you want an integer you would use a different division operator that is double slash let's run this program so we get 3 we also have modulus so that is the remainder of a division and finally we have exponent that is left ^ right so here 10 to the power of 3 'is a thousand now for all these operators here we have an Augmented assignment operator what do we mean by that let's say we want to add 1 to X we can write a statement like this so x equals x plus 1 or we can use an Augmented assignment operator so X plus equals 1 these two statements are exactly the same and what we have on the left side of the assignment operator can be any of these arithmetic operators here and one last thing before we finish this lecture in Python unlike languages like JavaScript or C sharp we don't have the increment or decrement operators so we don't have X plus plus or X minus minus in this lecture I'm gonna show you a few useful functions for working with numbers so let's set X to 3.14 or actually let's rename this to PI note that here I have used uppercase letters to indicate that this is a constant in Python unlike languages like C sharp and JavaScript we don't have constants we only have variables so if we define this there is nothing that stops us from changing the value of this variable so by convention we use uppercase letters to tell other developers in the team that this pi is a constant and it shouldn't be modified now let me show you a few useful built-in functions to work with numbers if you want to round the number you can use the round function so let's pass PI here and print it so we get 3 we have another useful function ABS short for absolute and it returns the absolute value of a number so if you had a minus sign here when we print this will get 3.14 here you go now to see the complete list of built-in functions in Python here in Google search for Python 3 make sure to add the version number and then add built-in functions on this page you can see all the built-in functions in Python now in this list we only have a few functions to work with numbers if you want to perform complex mathematical computations we have a separate module for that that's the math module so back to our code on the top first we need to import the math module now mass is an object with a bunch of useful methods for performing mathematical computations so here we can use the dot notation to see all these methods available to us for example you can use mass dot floor to get the floor of pi and this returns -4 because here we are using a negative sign if you want to see the complete list of functions or methods in the math module search for Python 3 math module here on this page you can see all the functions and their description quite often when we receive input from the user that input comes as a string and there are times that we need to convert that string to a different type here is an example we have this built-in function input we can add a label here like X this returns the users input as a string so we store it in this variable now let's imagine why should be X plus 1 now when we run this code we're gonna get an error let me show you don't run this using the code runner because code runner runs this code in the output window which is read-only so you won't be able to enter a value so open up the terminal by pressing ctrl + bhakti and run Python different windows or Python 3 if you're on Mac I've got PI let's add one here look we get this error type error this is happening because Python doesn't know how to interpret this expression because here we have two different outcomes if X is the string one one outcome is to convert this other operand here to a string and the result would be 11 the other outcome is to convert X to a number so we'll have 1 plus 1 and the outcome will be 2 so Python doesn't know how to do type conversion here and that's the reason we say Python is a strongly typed language because it doesn't do any implicit type conversion on your behalf you have to explicitly tell Python how you want your objects to be converted to the right type Java Script on the other hand is a weakly typed language so it does perform implicit type conversion for you now to solve this problem we need to use one of the built-in type conversion functions we have int float pull and stir or string now in this case we don't need to use string here because we already have a string and there is no reason to convert a string to another but there are times that you may want to convert an object to your string so just be aware of this function now let's take a look at what this functions return and let's delayed line two because this is the bad boy here save the changes back in the terminal let's run the application one more time and enter one so here's what we get number one as an integer one point zero which is a float and true so int and float are pretty self-explanatory but bull requires a little bit more explanation because in Python similar to JavaScript we have this concept of truthy and falsy values so here are the list of false e values empty strings number zero empty lists and none which is an object that represents the absence of a value this is exactly like null in C based languages so if we have any of these values and we try to convert them to a boolean using the bull function the result will be boolean false anything else would be true let's take a look at a few examples so here in the interactive shell I told you that number zero is considered false II so when we convert it to bool we'll get false any other numbers are true or true the-- so here's an example bula one is true if we add a negative number we also get true ask for strings an empty string is false e so we get false any other strings is truth e so even if I had the string falls here the result is true because this is a non empty string so here are the faulty values in Python whenever these values are used in a boolean context they will be equivalent to boolean false alright now let's talk about conditional statements so I'm going to start by defining a variable H and sending it to 22 now let's see if H is greater than or equal to 18 so in Python we have these comparison operators just like the other languages that you have worked with we also have equal and not equal now let's rewrite this back to greater than or equal to 18 now here's an interesting fact about Python in Python we don't have braces which means we're not gonna spend two decades fighting over where to put this braces shall we put them here or here no more nonsense like that it's over that's it no more so instead we put a colon at the end of this line now note that when I press ENTER this cursor is automatically indent so we use indentation to specify a code block here we can add a print statement adult we can have another print statement this is also part of this block now to terminate this block we simply remove the indentation now here we can have zero or more elseif blocks in python we call them Elif here we add another condition like if H is greater than or equal to 13 once again we have indentation let's print teenager and finally optionally we can have an else block once again colon print with one or more statements in this case we want to print child finally we'll have let's say all done now note that currently we have two spaces for indentation but when I save the changes auto-pay page kicks in and reformat our code according to pay paid according to pap 8 we should use four spaces for indentation take a look save the changes now we have four spaces you can also use tabs but only if you're maintaining a code that is written with that style if you're starting a new project prefer four spaces as the standard but you cannot mix tabs and spaces in Python three that's not allowed now let me show you a shortcut so here in a new file let's just type if look at these three items with this square icon these are code snippets so here on if-else I press ENTER and this automatically generates this snippet this came with the Python extension that we installed at the beginning of the course so here you can change the condition to whatever X is greater than one what is this past keyword this is basically a statement that doesn't do anything it's here purely to fill this if block because we cannot have an empty if block like this I say have the changes look we have this red underlined here that is not valid Python code so if you want to have just an empty block you use the pass keyword in Python just like the other languages we have three logical operators we have the logical and the logical or and not let's take a look at a few examples so I'm gonna start by defining a variable name sending it to Maj now let's say this is the input that we get from the user we want to check to see if name is an empty string how do we do that well earlier I talked about the faulty values in Python so we have 0 empty of string nan and an empty list these are all considered false e so let's talk about an empty string if this is interpreted as false then if we apply the not operator on it will get true right so to check to see if name is an empty string we can simply write a statement like this if not named color that's it print name is empty now let's run this program obviously we don't get that message however if I change this to an empty string and rerun the program we get name is empty but what if I add a white space here well white space is not considered true see because it's not an empty string so look if I run the program we don't get the message to fix this issue we can simply call dot strip method to get rid of all the white space now let's run it one more time beautiful so this is our not operator let's take a look at an example of ant so I'm going to set H to 22 now let's see if H is greater than or equal to 18 and age is less than 65 we say you are eligible good pretty easy right now here a question how do we write that expression in math we write it like this well more accurately we should add the equal sign here so age is between 18 and 65 right I have good news for you in Python you can simply write this expression that's perfectly fine this is what we call chaining comparison operators so we can rewrite this expression in a simpler and more meaningful way this is one of the reasons that Python is a highly popular language because the syntax is so clean without any clutter it's easy to understand and it comes with all these best practices and standards for writing clean code so let's rewrite this to 18 like this good now let's run the program obviously this person is eligible so here we have this piece of code similar to what we wrote in the last lecture if the person is 18 years or older we set the message to eligible otherwise we set it to not eligible in C based languages we have this operator called ternary operator that allows us to rewrite this piece of code in a more compact way let me show you how that looks like so we set message to we add our condition so if age is greater than or equal to 18 we add a question mark if that is true we set the message to eligible otherwise indicated by a colon we set it to not eligible if you have worked with C sharp JavaScript C++ Java you have seen this before if not don't worry let me show you the Python way so in Python we can rewrite this expression almost in plain English so message is eligible if age is greater than or equal to 18 otherwise it's not eligible isn't that easy so this is the ternary operator in Python in Python we have two types of loops so unlike some languages that have four or five different kinds of loops here we only have two types we have four loops and while loops their syntax is very simple and clean let me show you so we start with the four loops with four loops we can iterate over any object that is a trouble here are a few examples we can iterate over strings so for X in Python because strings in Python are a trouble which means we can iterate over them so in each iteration our loop variable X will hold one character let me show you so we terminate this line with a colon just like our if clauses now use indentation to specify the block of statements so we simply print X run the program this is what we get here's another example we can loop over lists so let's say we have a list of names a b and c colon print x there you go so we get ABC here now what if you want to loop over a sequence of numbers that's when we use the built-in range function let me show you so for x in we call the range function pass a number like 5 look at what happens now to keep this example clear I'm gonna comment out these few lines so the shortcut on Mac is command and slash on Windows is control slash now let's run this program so when we call range of 5 we get numbers 0 to 4 we can pass a starting number like 2 to 5 let's run this one more time so now we get to 3 4 we can also pass a third argument here called step let me show you so I'm going to change this zero to ten let's say we want to display all the even numbers between zero to ten so we passed two here that is our step now when we run the program we get zero to four and so on now one thing you need to understand about this range function is that it does not return and list let me show you so I'm gonna comment out these two lines as well let's just print range of 5 what do we see we see range of 0 to 5 we don't see a list object in contrast if we had a list like 1 2 3 4 5 see this is how we see a list printed in the terminal so what is returned from the range function is not a list it's a different kind of object it's a range object let me show you so here I'm gonna call the built-in type function now let's look at the type of this object it's an instance of a class called range so our range function returns a range object range objects in Python are iterable like strings and lists so we can use them in for loops now what is interesting about this range objects is that they take a very small amount of memory so here if we pass let's say 5 billion we are not gonna get a list of 5 billion elements you have a small object that can be iterated over in each iteration it will produce a new number like 1 2 3 4 and so on in contrast if we had a list of 5 billion items that list would take significant amount of memory so this is the difference between list and range objects so here we have a list of names let's write a simple program and check to see if you have a name that starts with J in this list so we can use our for loop for name in names now if name that starts with J perhaps we want to display a message like found now if this list has a million objects as soon as we find the first object we want to jump out of this loop we don't want to continue looping for performance reasons so this is where we use the break statement you have probably seen this before when python interpreter sees this statement it will terminate this iteration so now we jump out of this loop let's add another scenario to this program if we loop over all the names in this list and we don't find a name that matches our criteria perhaps we want to display a different message to the user like hey we couldn't find a name that starts with J so typically how we implement this in other programming languages is like this on the top we define a flag like found and set it to false then here as soon as we find an object that matches our criteria we set this flag to true and then after our for block we check to see if not found we print not found let's save the changes good run the program obviously we have a name that starts with J so found beautiful now let's change this to a John around the program not found so our algorithm is working properly but in Python there is a cleaner way to implement this scenario we don't need this found flag so let's delete it from here and here all we have to do is to get the same result is to change the statement to else so we have four else blocks in Python this else Clause is executed if our for loop completes successfully without an immediate break so if we iterate over all the objects in this iterable then this else Clause will be executed so now when we run this program we get the exact same result the other type of loose we have in Python our while loops so let's build a simple guessing game I'm going to define two variables yes set to zero and answer set to five now we can write a while loop like this while answer is not equal to guess once again : here we have indentation we can get the input from the user make a guess now as you know this returns a string so we need to convert this to an integer and then store it and the guest variable now as I told you before this code runner extension runs our code in the output window which is read-only so we cannot enter values there to fix this issue on the top let's go to preferences settings then click here and open settings at JSON now here we need to add a new setting that is code - runner that run in terminal by default it's false we need to set this to true save the changes now when we run this program using code runner it runs it in terminal so here in terminal window let's add a number like 1 2 3 4 as soon as we enter 5 the game stops so this is our while loop similar to for loops we have an else block here we can optionally use that this is only executed if the while loop completes successfully without using a break statement you to define a function we start with the keyword def which is short for define or function definition here you can see we have a few code snippets the first one is for defining a function so just press Enter so here's the basic syntax we start with a function name like increment now press tab in parenthesis we define parameters if they exist in this case let's have a couple of parameters like number and why so we want to increment a number by a given value right also you can see in this line is terminated by a colon and right after that we are using indentation to specify the body of this function just like our if and four classes now we can call this function like this so increment parenthesis give it a couple of values like two and three now note that when I save the changes you're going to see two line breaks after this function so save there you go so you have two line breaks because that's the style that pepp eight defines so we should always have two line breaks after our functions now these functions by default return the non or a null value so even though we don't have a return statement here this function is still returning a value let me show you so print the return value of increment and run the program look we get not now let's return a value like number plus by run the program again now we get five beautiful in Python unlike many other languages out there we can return multiple values from our functions we simply put them in parentheses so here we add parentheses let's say we want to return the original number as well as the updated number so number comma number plus PI now let's see what we get when we run this program serve run it so in parentheses we get two which is the original number and the updated number what is this this is what we call a top-up which is basically a read-only list so earlier in the course you have seen lists like numbers we use square brackets 1 2 3 this is a list we can add new objects to it we can remove existing objects a topple is like a list but we cannot modify it so we cannot add new objects to it we cannot remove existing objects now to convert this list with topple we use parentheses instead of square brackets okay delete another useful feature we have here is called keyword arguments so currently if someone looks at this code they may not be able to tell what exactly these arguments are for we can use keyword arguments to make our code more readable for example here we can prefix the second argument with something like this by equals now we can read this code like plain English increment two by three so this is what we call a keyword argument it's just a way to make our code more readable also similar to a lot of languages out there we can assign default values to these parameters for example we can set a default value for the by parameter so now we don't have to pass a second argument here and when we run this program the value of y will be set to 1 by default and one last thing before we finish this lecture earlier I talked about type annotation or type hinting we can use that feature in our functions as well so here we can annotate these parameters as well as the increment function itself so here we had : int for integer and here also : int and finally for the function itself before this : that terminus this line we need to add an arrow and then we'll add the return type of this function so integer as well now in this case we have a red underline here we i annotated this function to return an integer but I'm returning a topple so more accurately this should be topple save the changes and the error is gone there are times that you may want to pass an arbitrary number of arguments to a function here is an example let's say we have a function called multiply that currently takes two parameters a and B and this function would simply return a times B and then we can call it like this so far so good but what if you want to pass a variable number of arguments here like four and five well one way is to put these arguments in a list then we need to replace these two parameters with a list and we should also change the implementation of this function here we need a loop to iterate over this list and multiply all its elements that is perfectly fine however this syntax is a little bit noisy wouldn't that be nicer if we could pass these numbers or these arguments here without these additional square brackets let me show you how to do this so all we have to do is to prefix this parameter with an asterisk now let's print list and see what we get when we call the multiply function so save the changes run the program what do we get here we get a top hole because of these parentheses so when we add an asterisk before a parameter Python will see that parameter as a topple so when we pass an arbitrary number of arguments Python will automatically package them into a topple as I told you before a topple is like a list so we can loop over it get all the numbers and multiply them together let me show you real quick so we start by defining a variable total we set it to one next with a loop so for number in list : here we simply do total times equal number and finally we return total the changes good run the program actually I forgot to print the results so let's print it here run it one more time so here's the total in the last lecture you'll learn about the syntax for passing a variable number of arguments to a function we have a variation of this syntax and that's what I'm gonna show you in this lecture so let's start by defining a function call it save user here we add one parameter user but instead of one asterisk we use double asterisks so first let's print this user parameter here and see what we get when we call this function so save underline user now instead of passing an arbitrary number of arguments here we should pass an arbitrary number of keyword arguments remember keyword arguments name a codes value so here we can pass multiple properties about a user for example we can pass ID equals 1 name equals admin and so on so here we have two keyword arguments let's run this program and see what we get when we call this function I'll save the changes and run this is what we get look at the syntax here we have curly braces and in between them we have multiple key value pairs here's the first one here is the second one this is what we call a dictionary if you're a JavaScript developer this syntax is familiar too this is like an object in JavaScript now if you're not familiar with JavaScript objects or dictionaries in general don't worry later in the course you have a comprehensive section about data structures in Python and there I'm gonna cover lists tuples dictionaries and so on now to finish up this example here we can use square bracket notation to get the ID or name of a user let's run this program one more time so ID is 1 and name is admin beautiful in Python we have two types of variables local variables with the function scope and global variables with the file scope so in this example this message variable is a local variable in the greet function its scope is the greet function so we can access it anywhere in this function now in Python unlike languages like C sharp or JavaScript we don't have block level scope so if we define this variable inside of an if block it is still accessible outside of that block let me show you so here I'm gonna add if true colon inside of this if block you're defining the message variable but still accessible outside of the if block so here we can print message the same applies if we have a loop here a for loop or a while loop so in Python we don't have block level scope no matter where we define a variable in a function it is always accessible in that function after it is defined so that's all about our local variables now let's talk about global variables if we put this message variable outside of this function now it's a global variable so it's accessible anywhere in this point in any functions so here in the greet function we can print it on the terminal let's take a look so here recall greet run the program we get a now let me show you something interesting here the greet function I'm gonna assign a new value to the message variable let's set it to be run the program again obviously we get B however if I bring this print statement outside of this function and run the program again let's see what happens we get a what's going on here didn't we change the value of the message variable not really in this case this message variable becomes a local variable in the greet function because by default python enforces good programming practices as you probably know global variables are evil we shouldn't change them in a function because this can cause a side effect in other functions so in this case when python interpreter sees line 5 it will create a new local variable called message even though it has the same name as our global variable on line 1 these two are completely separate now I've seen some tutorials and books teaching you bad programming practices they show you how to modify the value of a global variable inside of a function so this is how we do it we use the global keyword and reference the message variable when Python interpreter sees this it will realize that in this function we don't want to create a local variable we want to use the global message variable that we defined earlier now if we run this code instead of a we're gonna get B because the changes will be visible after we exit this function and that is the reason I said you should avoid using global variables or if you really want to use them make sure not to modify them inside of a function because this can create a side effect in other functions maybe other functions rely on the original value of that variable so avoid using the global statement it's a bad practice it's evil alright let's finish up this section by looking at debugging in vs Co so I had this simple program with this multiply function that we talked about earlier if you want to follow along with me head over to bit Dudley /pi gist GIS T here on github you can see my guest simply copy paste this code we're going to use this code to explore debug in vs Co so below this function we have three statements to print start the result of calling the multiply function and print finish so to start debugging first we need to add a breakpoint so here on line eight you can use your mouse to put a breakpoint here or if you have taken any of my courses before you know that I always put a lot of emphasis on using your keyboard because professional developers use their keyboard not their mouse so using f9 you can add or remove a breakpoint now open up the debugging panel here on the top click this icon here this will create a JSON file called launch that JSON with a bunch of configuration for debugging you can see this file in the project folder inside of this vs code folder here is launched at JSON now you never have to touch this file we just have to create it the first time now let's close this back to the debugging panel now after this file is created in this drop-down list you can see various configuration options for a debugging session from this list select python current file integrated terminal so we're going to debug the current file in the terminal that is integrated inside of vs code there is also another one with an external terminal now to start a debugging session press f5 so here on the right side you can see my integrated terminal I'm going to close this because it's cluttering the view so so here is the breakpoint activate it now we are on this line we can step over eight by pressing f10 if you're on a Mac keyboard you should hold the function key that is on the bottom left corner of your keyboard so step over now on line 9 we are calling a function so we want to step into this function to see what is going on there for this press f11 now here we are inside of the multiply function on the left side inside the variables panel you can see the variables that are local in this scope so we have numbers which is the argument passed to this function let's step over one more time at f10 now we are at the beginning of our loop one more time f10 now at this point you can see a few other variables here so we have our total we have the current number that is picked in this iteration you can also create watches here if you want to look at the value of a variable that is not listed in this panel now let's say you inspected all the variables and you want to step out of this function to do that press shift and f11 now we are out back on line 9 f10 one more time and one more time and the debugging session is finished alright let's finish up this section by looking at a few very useful shortcuts for writing code fast first I'm going to show you the shortcuts for Windows users and in the next lecture we will look at the shortcuts for Mac so if you're a Mac user feel free to skip this lecture so here we are on line 9 and my cursor is right at the beginning of the line let's say you want to move the cursor to the end of the line instead of pressing the right arrow to go all the way to the end we can simply press the end key and here is the cursor or if you want to move the cursor to the beginning of the line simply press the HOME key there you go similarly if you want to move the cursor to the beginning of the file press ctrl + home here it is or ctrl + end/2 go to the end of the file now let's say we want to move this line up instead of cutting it from here and then copying it somewhere else we can simply move it up by pressing Alt + the up or down arrows or if you want to move these two lines up and down simply select them then hold alt and then up or down very easy now if you want to duplicate a line or multiple lines simply select them now hold down shift alt and then press a down key we can duplicate it as many times as you want there you go here's another useful shortcut if you want to convert this line or maybe these two lines into a comment simply hold down control and press slash using the same shortcut you can remove the comment so you can toggle it very easy and finally if you want to type the name of a variable or a function like multiplied you don't have to type all characters here are a few ways to type this quickly we can just type the first few characters and here in the intellisense you can see that so if you press ENTER this is what we call auto-completion here's another way so instead of writing the first few letters you can just pick any letters in sequence and type them so I can type mty or I can just type mpy or why there you go here it is so I hope you enjoyed these shortcuts and thank you for watching alright now let's take a look at the shortcuts for a Mac keyboard so here we are on line 9 and my cursor is right at the beginning of the line if you want to move the cursor to the end of the line instead of using the right arrow to go all the way simply hold down the function key and press right here it is or you can press function and left to jump to the beginning of the line similarly you can press function and up to go to the top of the file or function and down to jump to the end of the file pretty useful now let's say you want to move this line up instead of cutting it from here and then copying it somewhere else you can simply move it up by holding down alt or option and then pressing the up arrow or down very easy or we can select these two lines hold down the alt or option key move it up or down here's another useful shortcut we can convert these two lines into a comment by pressing command and slash and then we can remove the comment using the same shortcut so we can toggle it and finally if you want to type the name of a variable or a function like multiply you don't have to type all the letters like multiply that is very slow you can type the first few letters like mult and here in the intellisense you can see it's selected so press Enter or you can pick any characters in sequence and type them like mty here it is or we can type an py or m TP so you can abbreviate it any way you want I hope you enjoyed these shortcuts and thank you for watching one of the questions that often comes in programming interviews is the fizzbuzz algorithm you might be surprised that there are a lot of developers out there with even years of experience but they don't know how to solve this simple programming problem that's why I decided to include this in my course so let's see how this algorithm works and then you can spend 10 to 15 minutes on this exercise on your own so here we have a function fizz buzz that takes an input and depending on the input we give it it returns different results here are the rules if the input that we give it is divisible by 3 it will return the string fist let me show you so we run this program we get fizz if the input is divisible by 5 it will return buzz take a look here's buzz now the third rule if the input is divisible by both 3 and 5 it will return fizzbuzz so let's pass 15 here we'll get fizzbuzz for any other numbers it will return the same input so if I pass 7 it's not divisible by 3 or 5 it will return 7 itself so spend 10 to 15 minutes on this exercise you will see my solution next all right let's see how we can solve this problem so we get the input and check to see if input is divisible by 3 then we can set a variable like result to phase now let me temporarily simplify these rules because I want to show you a really cool technique so let's imagine if the input is divisible by 3 we'll return fizz otherwise we'll return bus so elves : we set the result to buzz and finally we'll return this result variable this is one way to implement these rules but it's not the best way there is a better and cleaner way let me show you so instead of defining this result variable and then returning it we can simply return this string here and also here and then we can get rid of line six so we remove one unnecessary line of code this was one technique the other technique I want to show you is when you have an if statement and in your if block you're returning a value you don't really need an else clause because if this condition is evaluated to false the control moves to the else clause and all we're doing here is returning a different value so this is the only possible outcome so here we can remove this else clause and simply return bus so with this technique I remove an unnecessary indentation as well I've made our code more linear okay now let's go back to our original algorithm so if the input is divisible by three we'll return fizz now we check to see if the input is divisible by five we'll return buzz so here we don't really need an Elif because if this condition is false we'll get here anyway so we can check if input is divisible by five we will return buzz once again if this condition is false the control moves here now we check to see if the input is divisible by three and it is also divisible by five then we will return fizz buzz now this expression is a little bit long I would prefer to make it more readable by putting parentheses around the first and second parts like this that is cleaner now if this condition is also false the control moves here that means our number is not divisible by three or five so we should simply return input once again we don't need an else or another if we simply return the input now let's run this program and see if it's working properly or not so we call our function with three and we get fizz beautiful let's call it with five we get Buzz perfect what if we call it with 15 we should get fizz bus however we get fees what is going on here the reason this happened was because when we pass 15 here line two is executed obviously 15 is divisible by three so that is why we immediately return fizz to solve this problem we need to move this condition which is more specific to the top so I've selected these two lines using alt + up I move these lines up beautiful all right now let's run the program one more time so we get fizzbuzz once again let's test it with three now we get fares let's test it with five when writing functions don't assume that your function is working make sure to test it with all different kinds of values let's test it with five we get Buzz beautiful what if you pass seven which is not divisible by three or five we get seven beautiful so what you see here is the simplest and most elegant implementation of the fizzbuzz algorithm and that brings us to the end of this section in the next lecture we're going to explore data structures in Python you're going to learn about lists tuples sets and dictionaries I hope you enjoyed this section and thank you for watching you you made it this far and that makes me think that you're really enthusiastic about learning Python so I highly encourage you to enroll in my complete Python course where we go way beyond this crash course you will learn how to use Python in real-world scenarios such as data analysis and visualization automating repetitive boring tasks that involve working with files and folders spreadsheets PDFs data compression sending emails web crawling consuming api's and much much more this course comes with a 30 day no questions asked money back guarantee and a certificate of completion if you're interested click the link below this video to access the course once again thank you for watching please support me by liking and sharing this video and also subscribe to my channel to get free new videos every week thank you and have a great day

Channel: Programming with Mosh

Views: 879,664

Keywords: python programming, learn python, python tutorial, python course, python crash course, code with mosh, programming with mosh, mosh hamedani, python for beginners, programming, software development

Id: f79MRyMsjrQ

Length: 108min 5sec (6485 seconds)

Published: Mon Oct 22 2018