Zip two list of lists together - Python

Question

There are a few questions on this but none relate to this. I have two separate list of lists that I want to zip together. The comprehension works for a normal list but not a list of lists.

X = [[17, 4]]
Y = [[32,-58]]

lst = [list(x) for x in zip(X, Y)]

Out:

[[[17, 4], [32, -58]]]

Intended:

[[17, -32], [4, -58]]

Vasilis G. · Accepted Answer · 2019-11-28 22:18:23Z

3

This should do it:

lst = [list(x) for x in zip(*(X + Y))]

What you want to do is, create a 2D list by merging X and Y and then transpose it using zip(*(X+Y)).

answered Nov 28, 2019 at 22:18

Vasilis G.

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3 Comments

jonboy Over a year ago

Thanks @Vasilis G. What does the * operator do?

Vasilis G. Over a year ago

@jonboy the operator * in used in a list of lists in order to unpack values of the outer list and use them as arguments for the zip function. In your case: zip(*(X+Y)) is zip(*[[17, 4],[32,-58]]) which will unpack the outer list and return zip([17, 4],[32,-58]). Then the zip function will be applied to those two lists.

jonboy Over a year ago

Aww ok. Makes sense. Thanks

Andy L. · Accepted Answer · 2019-11-28 22:34:12Z

2

You may also try this

[list(x) for x in zip(*X, *Y)]

Out[222]: [[17, 32], [4, -58]]

answered Nov 28, 2019 at 22:34

Andy L.

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