List comprehension equivalent to map on two lists in parallel

Question

I understand that with one list argument map() can be replaced by a list comprehension. For example

map(lambda x : x**2, range(5))

can be replaced with

[x**2 for x in range(5)]

Now how would I do something similar for two parallel lists. In other words, I have a line of code with the following pattern:

map(func, xs, ys)

where func() takes two arguments.

How can I do the same thing with a list comprehension?

Martijn Pieters · Accepted Answer · 2016-12-25T23:28:58.373

17

map() with multiple arguments is the equivalent of using the zip() function on those extra arguments. Use zip() in a list comprehension to do the same:

[func(x, y) for x, y in zip(xs, ys)]

Generally speaking, any map(func, a1, a2, .., an) expression can be transformed to a list comprehension with [func(*args) for args in zip(a1, a2, .., an)].

edited Dec 25 '16 at 23:28

answered Dec 25 '16 at 23:19

Martijn Pieters

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This answer is less thorough than the old, popular, canonical duplicate. – TigerhawkT3 Dec 26 '16 at 00:15
3

@TigerhawkT3: which I wasn't aware existed. Is this answer now being judged in comparison to a different question? – Martijn Pieters Dec 26 '16 at 01:00
You didn't think there was already a question about `zip`? – TigerhawkT3 Dec 26 '16 at 01:04
4

@TigerhawkT3: no, I wasn't aware there was already a question on how to translate `map()` with multiple arguments to a list comp, no. Was I supposed to? – Martijn Pieters Dec 26 '16 at 01:21

List comprehension equivalent to map on two lists in parallel

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