#4 Python Tutorial for Beginners | Variables in Python

[Music] welcome back aliens my name is Devin 20 and let's continue with this series on Python in fact in the earlier videos we have talked about what is Python we have we have installed two software's and we have also worked with certain operations right we had fun in the last session now in this video where I talk about what is variable but first of all why do we need one let's try something here so what I will do is I will go back to my previous example you know we were adding two and three so we have done with that right we are saying two plus three now if you remember in Matz what we do is we of course we work with numbers but then when it the moment you start with algebra you have this concept of using x and y so what we do is we say let X is equal to five can you do that here so we have X equal to 2 so I'm storing this value 2 in a variable called as X and that's a new word now what is variable so basically variable is a container where you can put your values example we are storing to here in a container and the name of that container is X of course you can give anything doesn't matter you can say ABC you can say a box you can give any name right so we can say X equal to and the moment I say enter now this is the first time when you say enter and you have not got any output right so in the earlier the prompts what we did is when we said any of any operation it was giving you some output here we have not got any output it's just an assignment operation so in assignment what we do is we have a variable name equal to our value so we are assigning to to X ok that works so can i you can I do this now can I say X plus 3 yes right because in X we have a value which is 2 oh it works you can see we got 5 that works can I store 3 as well let's try so I will say Y is equal to 3 now we have two variables x and y so we have two boxes and now I will say X plus y oh it works right it works so we can say X has two y as 3 and we are adding them ok so that's why we can we can use them but why they're police variables now normally when you say variable this term simply means you can change the value can be changed here can I say equal to nine can I change the value from two to nine let's try and then when I say enter oh it works that there was no error but now if I try to do this if I say X plus y X will have a value which is two or nine that's a question because we are changing it but there is no error enter oh you got 12 that means the value of x now is 9 okay so we can change the value and now we can justify that what has variables right so what is variable it's a box but it can have a value now do we need to define the type of the variable you don't need to so the moment I assign a value it you can it automatically takes whatever value you are assigning so in this case it is integer now that let's do this thing what if I say X and if I say enter what it will do so the moment you say X and enter it will print the value of x in this case which is 9 right what if I use a variable ABC now of course we have not defined this variable right and we are still trying to use it now we can say Enter key got an error the other is it says name error ABC name ABC is not defined and that's why we have not defined ABC yet so if you argue if you're using a variable which is not defined so it will of course give you an error now I will do one more thing I will say X plus 10 so of course it will give you 19 now what if I want to add 19 with y I mean something this is something in this way I would say 19 plus y but then if you think about this 19 this is the output of the previous operation right now if you want to use the output of the previous operation we can use underscore so underscore represents the output of the previous operation and if I say enter you can see record 22 so it is 19 plus 3 which is 22 so they won this works right so this is amazing you know there are so many things you can you can work with this so we can use variables for for numbers right so we can use it for float all integer what about string can I use names with can I use variables with string or the string variable let's try so I will put a variable as name and I will use a name as YouTube and if I say interro it works and if I print name we got YouTube so it is perfectly working so we can use string as well so example I can say nay plus you two blocks so you can you can see the car due to block so it is name which is YouTube plus rocks okay this p1 this work that's perfectly fine in fact let me just do an experiment can I say name and space dogs okay this is not working so you have to make sure that you put plus there because if you have plus then put then then only it will try to interpret that but there's this one thing which is very fancy here you know so we talk about YouTube it's a string right and it's a combination of characters that means even if I want to fetch one character it should be paper we should be able to do that right and yes we can do that so if I say name and if I want to fetch one character how will I do that so let's say if I have a YouTube here and YouTube has seven letters or seven characters if you when you break it down it will create an array or you can say collection of characters the numbering starts with zero because normally in computer's numbering always starts with zero so here if you want to fetch it we have to use a square bracket and you have to mention 0 so we are specifying hey I want to fetch the first letter of names in this case it is y how it works so now I will fetch the last one which is 6 which is e in this case and we got e that works now I will fetch let's say 8 see we don't have eight we don't have nine characters why do we only have seven characters so the first one is 0 the last one is 6 how about 8 the moment you do that it will give you an error it says index error string index out of range of course you are going out of your limit right so you cannot do that ok can I use negative numbers let's try I will use minus 1 so I want to I want your guess here what you think it what it will do come on think about it ok so let me just ain't any time let's see what happens so when I say enter you got e ok so the answer is when you say minus number it will start from right to left ok so it will it will start with the ending so we just a in this case that means if I say minus 2 it will give you the second last data which is B that's right and if I say minus 7 which will be the first one right which is why oh it was it goes in reverse order now now what if I want to print to gag does not want to so let's say I want to print Y and O so in this case I will say name and I will start with 0 of course we want to print 0 the first character and the second guy to write that means we will give 2 now this to doesn't means number of characters it means the ending so I want to start with 0 and 1 so first two characters and you can see regard to y 0 the same thing if I do it for 1 colon full so come on guess so 1 means second character right so it will start with O and it will end at 3 because you cannot include 4 so it will it is exclusive of fold so it is 1 which is o U and T oh it works we got out yes yes it works now what if I specify only one and colon if I don't specify the ending what happens in this case it will start with 1 and it will come it will go till the end okay that has well so if you don't specify the ending part it will go in that way what if I specify the ending part but not the starting point example if I say if I if I keep it blank and after : I will say for now in this case it will start with the first later and it will end at 3 which is before 4 and that's why you got Y or u T so this fun right ok what else we can do here what if I specify name and I will give the wrong values I would say 3 : potatoes of course we don't have 10 characters right now in this case it will end at the last one which is available so it will not give you any other in this at this case you can see we got tup e to start with T and then its end at e because we don't have any other character so if you don't if you want to avoid errors this is what is one way okay now can I change the later example I don't want it to be YouTube I want to I want it to be my tube so I will say name from 0 to 3 I want to change this with my can I do that so I'm changing y-o-u to my the moment I say enter you got an error it says string object does not support item assignment so the thing is once you assign the value you cannot change it not you want for one character if I say 0 I want to change the first character to brought you even this will not work you can see we got the error so you not change the value that means strings in Python is immutable you cannot change the value of it that's awesome right but then that doesn't means you cannot you cannot change while printing example if I if I want to plant my job you can do that so first I will print my and then I will give up I will give a space and then plus I want to print cube right so in that case I will say 3 : 6 4 maybe the ending part doesn't matter so you can see we got my tube if you don't want space you can do that you can say my and then without space I can type it too so this works yeah so this is how you work with the string you work with variables right you can have a number of variables you can have a float variables and you can have a string variable as well in fact which string we have one more thing let's say if you define a string which is let's say my name is a variable and my name here is Naveen ready and if I want to know the length of my name we can do that so we have a Len function and we can pass my name as I as I mentioned there are some inbuilt functions available in Python and one of them is left Len so you can see we got 11 characters so yeah that's it that's it from this video we have talked about different variables assignments and stuff so I hope you are enjoying my session let me know in the comments section and they don't even like button if you're enjoying it thanks for watching everyone you

Channel: Telusko

Views: 3,200,665

Keywords: telusko, navin, reddy, tutorial, java, python, variable, what, why, need, assign, value, fetch, print, operation, string, int, double, find, length, function, index, number

Id: TqPzwenhMj0

Length: 10min 22sec (622 seconds)

Published: Tue Jul 03 2018