Intermediate Python Tutorial #3 - Map() Function

Key Takeaways

hey guys and welcome back to another YouTube video in today's video this is the third video in our intermediate Python tutorials and I'm gonna be going over the map function so pretty much the map function is an extremely useful tool that allows us to apply a function to a list and then create a new list with those new values and you'll understand what I mean as I go through an example here so before I even start using the map function I want to just present us with a problem the map function consult and this is kind of the best way to understand it so I'm gonna create a list which we call it Li of integers up to 10 like this so 9 9 10 ok and now I'm going to create a function and I'm gonna call it funk and it's simply gonna take one parameter X and all we're going to do is we're gonna return X to the exponent X very simple okay now what this problem is it's very simple um I want you or I want to be able to apply this function X to every value in the list here so 1 to 10 and then have that stored in a new list so intuitively the way that you would want to do this or the way that you would try to do this at least is you make something like a list is you go to this you'd write a for loop say for X in Li and then you say new list dot append and then you would put well funk and X like that and then if you printed out your new list you would get that value I don't know why print just showing up in a different color now but anyways and there we go so we get one for 27 and so on and so forth ok so now what we want to do is use the map function to do this faster so this is a very valid way to do this this works fine but I can actually shorten all four of these lines into one by using the map function so let's go ahead and do that now so I'm going to start by typing it uh actually we're just going to print because I want to print it first starting with I'm gonna do list like that and I'll tell you why in a second I'm going to my map function like so and now your map function takes two arguments so it takes a function and it takes a list so let's give it our function which in this case is gonna be called func and then let's give it our list so I actually don't need these double brackets here and excuse me let's give it our list which in this case is Li so let's talk about what this really is doing right now so the map function takes a function which is funk so the name of our function and it takes a list which is Li what it's going to do is it's going to apply this function to every element in the list and we can watch this happen we run the program and you see we get the exact same value as we did before and that's extremely extremely useful in Python because there's a lot of times you want to apply a function or even possibly multiple functions onto a very onto a list or every element of the list and you don't have to type out a whole for loop yes you can do that it works fine but the map function is just a shortcut to be able to do that so let me just show you now maybe a few other examples that we can use so like using this map function there's another way that we can create this and it's totally preference which one you want to use I like using map just because it's kind of cool you can also use wink a list comprehension and this is something I would have shown in some of my previous Python tutorials like from way back like years ago on my channel but I'll go over it quickly now and the way that this works is you can do the same things you can say func X for X in Li now this is actually going to give us the exact same value as what we have up here with this map function Li for example because what we're going to do is we're going to say we're gonna take this right here so whatever this expression is and we're gonna do it for every value of x in the list so that's exactly what this map function does and this is gonna turn it into a list because we put our square brackets here so I print this out see we get again the same value and that's how list comprehension works now for a list comprehension you can also add like an expression anywhere so it can do something like if let's say X modulus which modulus 2 equals equal to 0 and now it's only gonna do this we're put this into the list if X is divisible by 2 syntax error oh I forgot my square bracket here my bad don't know how you even got rid of that that's friendly oh that's cuz that is why all right excuse me on that okay so now we get 4 2 5 6 so it's only doing it for the even numbers of X so yeah those are two really cool ways to kind of change a list or modify them apply a function to them in Python say obviously you might want to use a function that's more advanced than this this is just for a basic example and if you wanted to apply maybe two functions to it you could have X to be changed here and then you could return like function two of X to the X here and then that would put that value obviously in the map so again map takes two parameters a function and a list and it will apply the function to every value in that list I hope this has been useful for you guys if you did enjoy the video please make sure you leave a like and subscribe and I'm going to be moving on to some more complicated and other examples using map and other functions in the next video so make sure you stay tuned for that [Music]