CODEWITHSUNDEEP
python
Kazz
Kazz

Reputation: 616

Python built-in function

is there a build-in equivalent of such function in python:

def foo(a_func,a_list):
    if len(a_list)==2:
        return a_func(*[a_list])
    else:
        return a_func(a_list[0],foo(a_func,a_list[0:]))

in other words foo(lambda x,y:x+y,[1,2,3,4]) would add 1+2+3+4 and foo(lambda x,y:x-y,[1,2,3,4]) would do ((1-2)-3)-4 etc.

And i know you can make it faster and prevent stack overflow ( :D ) but i think i remember such function but have no idea what the name is and dunno what to google.

Upvotes: 3

Views: 134

Answers (3)

Martijn Pieters
Martijn Pieters

Reputation: 1122142

You are describing the reduce() function; in Python 3 it has been moved to the functools module:

Apply function of two arguments cumulatively to the items of sequence, from left to right, so as to reduce the sequence to a single value. For example, reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) calculates ((((1+2)+3)+4)+5).

You can of course use any callable; the operator module offers several handy options:

>>> from functools import reduce
>>> import operator
>>> reduce(operator.add, [1,2,3,4])
10
>>> reduce(operator.sub, [1,2,3,4])
-8

Upvotes: 2

Alex Martelli
Alex Martelli

Reputation: 881705

Looks like you're looking for https://docs.python.org/2/library/functools.html#functools.reduce (AKA https://docs.python.org/2/library/functions.html#reduce in Python 2), assuming there's a bug in your code and by a_list[0:] you actually mean a_list[1:] (otherwise you're looking for a never-ending loop:-).

Upvotes: 2

Kasravnd
Kasravnd

Reputation: 107287

Its what that reduce function is for!

Apply function of two arguments cumulatively to the items of iterable, from left to right, so as to reduce the iterable to a single value

Upvotes: 3

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