The zip() function takes a number of
An iterable is an object that contains elements over which you can iterate. Examples are lists, sets, or tuples.
Before I’ll explain it slowly to you, try out the code in our interactive shell:
Say, you have two lists:
Now you zip them together and get the new list:
[(1,4), (2,5), (3,6)]
You can unzip them by using the following trick: If you remove the outer bracket of the result (e.g., via the asterisk operator), you get the following three tuples:
(1,4) (2,5) (3,6)
When you zip those together, you get the new list:
So you (almost) have your two original lists again!
This is the idea in the following code snippet:
lst_1 = [1, 2, 3] lst_2 = [4, 5, 6] # Zip two lists together zipped = list(zip(lst_1, lst_2)) print(zipped) # [(1, 4), (2, 5), (3, 6)] # Unzip to lists again lst_1_new, lst_2_new = zip(*zipped) print(list(lst_1_new)) print(list(lst_2_new))
The rest of the article is about answering any question you may have regarding the
How to Zip Lists of Different Lengths?
Just do it. Python simply ignores the remaining elements of the longer list. Here is an example:
print(list(zip([1,2,3],[1,2]))) # [(1, 1), (2, 2)]
Can You Use Zip With a Single Argument?
Maybe you remember that I did this a few emails ago to trick you. So: Yes, you can do that. Python still creates a tuple of the
print(list(zip([1,2,3]))) # [(1,), (2,), (3,)]
This strange output formatting caused some confusion. Many students of my free email course stumbled upon it (join us if you want to continuously improve in Python —
I hope that you now understand completely that this is not a bug in Python but only a tuple with a single element. (Don’t ask me why they didn’t use the format ‘(x)’ instead of ‘(x,)’.)
What’s a Zip Object in Python?
You will quickly realize that the result of the zip function is neither a list nor a tuple:
x = [[1,2],[3,4]] print(zip(*x))
You would expect [(1,3),(2,4)] but the result is “<zip object at 0x000002E9D87CFD08>”. That’s weird, isn’t it?
Actually not. The result of the zip() function is an iterator. An iterator in Python is an object that contains a fixed number of elements and allows you to access each element in an ordered fashion (the next(iterator) function for an iterator). This is more efficient and more general-purpose — compared to creating a list and returning the list as a result.
To fix this, you have to convert the iterator object in the iterable you want (e.g. set, list, tuple):
x = [[1,2],[3,4]] print(list(zip(*x))) # [(1, 3), (2, 4)]
Finally, let me clarify one last thing: the asterisk operator is placed just before the iterable to be unpacked (not after it or anywhere else). If you put the asterisk operator anywhere else, Python will think it’s multiplication and throw an error (best case)
x = [[1,2],[3,4]] y = zip*(x) # NO! y = zip(x*) # NO! y = *zip(x) # No! (It's an iterator not an iterable) y = zip(*x) # Yes!
Where to Go From Here?
Enough theory, let’s get some practice!
To become successful in coding, you need to get out there and solve real problems for real people. That’s how you can become a six-figure earner easily. And that’s how you polish the skills you really need in practice. After all, what’s the use of learning theory that nobody ever needs?
Practice projects is how you sharpen your saw in coding!
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Then become a Python freelance developer! It’s the best way of approaching the task of improving your Python skills—even if you are a complete beginner.
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