Python – Useful code which uses reduce()?

functional-programmingpython

Does anyone here have any useful code which uses reduce() function in python? Is there any code other than the usual + and * that we see in the examples?

Refer Fate of reduce() in Python 3000 by GvR

Best Solution

The other uses I've found for it besides + and * were with and and or, but now we have any and all to replace those cases.

foldl and foldr do come up in Scheme a lot...

Here's some cute usages:

Flatten a list

Goal: turn [[1, 2, 3], [4, 5], [6, 7, 8]] into [1, 2, 3, 4, 5, 6, 7, 8].

reduce(list.__add__, [[1, 2, 3], [4, 5], [6, 7, 8]], [])

List of digits to a number

Goal: turn [1, 2, 3, 4, 5, 6, 7, 8] into 12345678.

Ugly, slow way:

int("".join(map(str, [1,2,3,4,5,6,7,8])))

Pretty reduce way:

reduce(lambda a,d: 10*a+d, [1,2,3,4,5,6,7,8], 0)