Cartesian product of two lists in python

Cartesian product of two lists in python

list1 = ['a', 'b']
list2 = [1, 2, 3, 4, 5]

Expected Output:

list3 = ['a1', 'a2', 'a3', 'a4', 'a5', 'b1', 'b2', 'b3', 'b4', 'b5']

Answers:

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Method 1

Do a list comprehension, iterate over both the lists and add the strings, like

list3 = [i+str(j) for i in list1 for j in list2]

Method 2

If you are using Python 3.6+ you can use f-strings as follows:

list3 = [f'{a}{b}' for a in list1 for b in list2]

I really like this notation because it is very readable and matches with the definition of the cartesian product.

If you want more sophisticated code, you could use itertools.product:

import itertools

list3 = [f'{a}{b}' for a, b in itertools.product(list1, list2)]

I checked the performance, and it seems the list comprehension runs faster than the itertools version.

Method 3

You could use itertools.product function:

from itertools import product

list3 = [a+str(b) for a, b in product(list1, list2)]

Method 4

if you’re not familiar with list comprehension you could also use

list3 = []
for l in list1:
    for b in list2:
        list3.append(l + b)
print list3

this will do the same exact thing, but using the list comprehension from above would be the best way

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0