What Does "yield from" Do in Python?

Key Takeaways

what is going on guys welcome back in this video today we're going to learn what the yield from statement does in Python so let us get right into [Music] it all right so this is going to be a pretty short video today we're going to learn about the yield from statement in Python what it does and how to use it now for those of you who don't know what the yield keyword does in the first place it's a keyword used in generators to produce values to generate values or as the key says to yield values you can maybe compare it to a return statement but it's not quite the same because it produces values on demand here now let's look at a simple example let's say we have a function generator and this function has a couple of yield statements in it so yield one yield 2 and maybe something like yield hello world you can put any python object here basically now what we can do is we can create this generator we can say gen equals generator and then we can get the next value from the generator on demand so we can request the next value or we can also iterate over it and automatically request the next value so I can do something like print next gen and this is going to give me a one because that's the first yield statement here and if I do it three times I'm going to get one two and hello world if I do it another time I'm going to get uh a stop iteration exception there you go because there are no longer any values that are yielded and of course this can be be done in different ways we can do things like 4 I in range 10 you can yield I this also works then I'm going to get one two hell World 0 one 2 3 and so on I can also add conditions but that's the basic idea we have this generator function and the yield statements are uh producing values one after the other and this makes sense in a couple of use cases if you want to basically have the values on demand as I said now what does the yield from keyword do here what does it mean to go and say yield from and then something after it this is a python statement a python keyword combination that does something so what can we do here now what we can do here is we can basically pass any iterable so in a most simple way here I can just go ahead and say yield from 1 2 3 4 5 so let's delete all of this this is a possible thing in this case I would just yield the values from this collection so I would get these numbers here and I would yield them one after the other 1 2 3 4 5 but usually what you want to do is you want to have a generator and you want to have another generator function that yields values from a generator that we have defined before so I can have here uh def other generator and let's say up here I have I don't know yield one yield two yield three then in this other generator function here what I can do is I can yield my own values I can yield something like hello world and I can also yield something like goodbye and in between I might want to yield the values all the values from generator so what I can do here is I can say yield from generator and this is of course nice because an alternative way to write that if you don't use yield from is to say for Value in general generator yield value so that's basically the functionality here instead of having to write this explicitly as a loop instead of iterating actively over the generator we can write a simple short form we can say yield from generator and that has the same effect um in this case of course we need to say other generator then we're going to get Hello World 1 two 3 and if I add one more here we're going to also get goodbye that's the basic idea here now you need to consider that everything you pass here after a yield from statement will be treated as an iterable it will be iterated over which means that some things that are not necessarily lists can still be treated as iterables if you just yield hello world you're going to get hello world if you yield from Hello World hello world is considered an iterable which it is every string is an iterable so what we can do here is we can yield the individual letters so what happens here basically is you get h e l and so on and of course you don't have to do it like this you can also iterate over to the generator you can say for uh value in gen print value then you get all the values but this is how the string is yielded if you use a yield from because it's considered to be an iterable so yeah that's basically it this is just a short way of yielding from iterables this can be as I said a generator a string a list whatever anything that's iterable can be yielded with yield from so that's it for today's video I hope you enjoyed it and hope you learned something if so let me know by hitting a like button and leaving a comment in the comment section down below and of course don't forget to subscribe to this Channel and hit the notification Bell to not miss a single future video for free other than that thank you much for watching see you in the next video and bye