How can I 'unzip' a list in Python?

Question

Let's say I have two lists:

a = [1, 2, 3, 4]
b = [5, 6, 7, 8]

Based on a, I want to remove the value at that index for both lists if it's even. I thought of using a zip:

c = [i for i in zip(a,b) if i[0] % 2 == 0]

But now how can I turn [(2, 6), (4, 8)] back into two separate lists? As:

a = [2, 4]
b = [6, 8]

Obviously I can use two list comprehensions, but I was curious if it's possible to do that in one line with some built-in python function. Something like:

a, b = somefunc(c)

@wim I'm so dumb, I never knew that was a thing!! Thanks for showing me the light! — Shane Smiskol, Oct 10 '19 at 01:38

score 1 · Accepted Answer · edited Jun 27 '23 at 18:31

1

You can use zip again

a = [1, 2, 3, 4]
b = [5, 6, 7, 8]
a, b = zip(*[i for i in zip(a,b) if i[0] % 2 == 0])

See this answer for more details on why zip(*...) undoes zip(...).

edited Jun 27 '23 at 18:31

Josiah Yoder

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answered Oct 10 '19 at 01:37

meTchaikovsky

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Worked perfectly! Thanks! – Shane Smiskol Oct 10 '19 at 01:47

How can I 'unzip' a list in Python?

1 Answers1