Sometimes you just want to update the same
line with new text without going down one line. In today's video we're gonna have
a look at how you can do that Alright guys so I'm gonna start by
importing "time" which we're gonna use and then I'm gonna print a few things normally, so "hello" and time.sleep two seconds, print "I am Fabio", time.sleep and then, last one So, let's just have a look at how python
does that normally without changing anything so I'm going to save the file, open the
terminal and then we're gonna run python overwrite lines. So let's
have a look, "hello I am Fabio welcome to my channel", so this is actually the
default way. So let's clear and keep going so If you want to actually show these messages,
without actually changing line, so actually overwriting the previous one, you need to use the
carriage return. So basically the carriage return moves the cursor at the beginning of the line
so that the new string will be printed from the beginning of the line, overwriting the previous
one. So the carriage return is this character, this alright. So what's gonna happen here
is that python actually prints the hello and then as there's this carriage return
the cursor will move from the end of hello to the beginning of the string, so it's gonna
move here and then it's gonna print "I am Fabio" overwriting the "hello", the same thing down
here. So let's have a look save the file and then I'm going to run this So as you can see it's not working so why isn't
it working? Well, because print has an argument, a keyword argument, which tells python what to
add at the end of each string printed. The default one is the line feed and the line feed is like
hitting enter so the cursor goes down one line automatically, so we need to fix that. So to
fix that we actually need to change that end like that like that and like that. So basically here we are
telling python that we don't want anything printed after the string. So the default one is actually
this one, so we're gonna delete that and leave an empty string as value, so it's not gonna
actually print anything. So I'm gonna save the file and see how it works, so, I'm going
to leave it like that, let's have a look. As you can see, we just have the last one
because all the others have been overwritten, perfect. There is still a problem when the strings
that come after are shorter than the previous one, so let's have a look at what I mean.
So I'm gonna just comment these out, I'm gonna write, I'm actually going to copy this uncomment it and change a few things, so do this.
So now I'm gonna make this longer, so "Hello I am Fabio", this a little bit
shorter like "welcome" and then even shorter "here". S o let's
have a look at how it works pull up the terminal. So I'm going to
clear this and let's see what happens It doesn't look right to me
so why is this happening? So basically when the cursor moves from the
end of the line to the beginning of the line, then it writes the string but the other string
is sort of beneath. So for example "welcome" has this length, so one two three four five
six seven characters, that means that seven characters are going to be overwritten but then
the remaining part is gonna stay there, because the cursor is actually here and then there's the
"welcome" here and "here" has only four characters that means that "welk" is going to be overwritten
but then the "ome" is not going to be overwritten, so as you can see here "ome I amFabio". So how can
we actually fix this? There's a really simple way, so I'm going to show that to you right now. So you
just need to add spaces at the end of the actual string, so if you do something like this, just
random number of spaces. So now the actual string is this long, so this is definitely longer than
this, so all the spaces here are gonna overwrite the remaining part of the string and the same
down here. So let's have a look at how it works As you can see now it's working properly and how
it's supposed to work, so you can actually do a thing like that I'm gonna
just copy and paste them Down here and comment these out. You can actually
add spaces in a different way so you can do like, spaces, and then do something like, times 10,
so 10 spaces and then you can add them at the end of the string so you can delete this and
you can do like, plus spaces and the same here, you can do whatever you want to do, but I
mean, this looks a little bit better to me, it's just my personal preference,
so let's see if it still works let's see Perfect! Really important thing to know is that
this method works only if the terminals width is greater than the length of the string, otherwise
if the terminal has the "wrap text" enabled, which is like a setting, the string is going to be cut in two or more lines and it won't
work properly because the cursor is like, let's say on the second line and the new string
will overwrite only the line and not the one above. So maybe if I show you an example you'll
understand that better so that's what I'm gonna do So let's clear this up so let's make this string
really really long I'm just gonna add like things like that you know just to write something, so I'm actually
making the strings really really long so they are actually gonna wrap, I'm going
to save the file, so let's see what happens. So I'm gonna just narrow the terminal
like that, let's try that out Here what happens is that, this is the first
line, maybe the first line is like up to here but then the "welcome" has overwritten
the third line so actually the cursor probably was here and then it started from the
beginning of this line and then overwrote this line with the welcome and then it went down
here, this is actually the welcome string, but then the cursor was here and then it
went here and started writing here like that and then all these spaces right so
it's not actually working properly because the cursor wasn't on the same line. So
the cursor needs to be on the same line to work otherwise it'll start from this line and then
start from the beginning of this line, not actually this line. Hopefully that makes sense,
so be careful when you are actually dealing with things like that because you need to have the
terminal's width greater than the length of the string or maybe you need to make sure
that the terminal doesn't have the wrap text enabled and then the thing is gonna work
properly because actually the text won't wrap, so the line is gonna be the same every time.
So hopefully that makes sense so I'm just gonna do this i don't really like
that I just did it to show you and now I just want to actually have a look at
another little example, so let's comment this out and then let's have a look at, I
don't know like, I've got a number and I want to print all the numbers up to, don't
know like, 100000 yeah and then I'm going to print carriage return then, "format", then I'm going to use the n, the number, "n" like that then here
I'm going to actually add one to the number, save it and let's see what we've got, I'm
gonna clear clear this let's have a look So this is actually a little example to show
you how you can use things like that so you can actually count things and stuff like that. So
that's a way you can use the carriage return. So as you can see I just wrote the carriage
return here but you could have written the carriage return like here, at the end of the
string because: it prints a line and then at the end it adds the carriage return so the cursor
goes back to the beginning of the line and then it prints another string and then again the
carriage return, so either way actually works I'm going to save that, so I'm going to just
close everything as usual and that's it guys
