Pythonic way of converting a list to inputs of a function of several variables

Question

I'm beginning to feel a little dumb for not figuring this out...

say I have a function of two variables:

def testfun(x,y):
    return x*y

now I have a list of values, say [2,3], which I want to input as values into the function. What's the most Pythonic way to do this? I thought of something like this:

def listfun(X):
    X_as_strs = str(X).strip('[]')
    expression = 'testfun({0})'.format(X_as_strs)
    return eval(expression)

... but it looks very un-pythonic and I don't want to deal with strings anyway! Is there a one liner (e.g.) that will make me feel all tingly and cuddly inside (like so often happens with Python)? I have a feeling it could be something crazy obvious...

`testfun(*[2, 3])`? – Ashwini Chaudhary Aug 29 '14 at 15:47 — Ashwini Chaudhary, Aug 29 '14 at 15:47
dupe? http://stackoverflow.com/q/12786102/748858 – mgilson Aug 29 '14 at 15:50 — mgilson, Aug 29 '14 at 15:50
uum yes thanks! Wow, I can't believe I didn't know that :P – H. Arponen Aug 29 '14 at 15:50 — H. Arponen, Aug 29 '14 at 15:50

score 2 · Accepted Answer · answered Aug 29 '14 at 15:50

The * notation will serve you well here.

def testfun(x,y):
    return x*y

def listfun(X):
    return testfun(*X)

>>> testlist = [3,5]
>>> listfun(testlist)
15
>>> testfun(*testlist)
15

The * notation is designed specifically for unpacking lists for function calls. I haven't seen it work in any other context, but calling testfun(*[3,5]) is equivalent to calling testfun(3,5).

Pythonic way of converting a list to inputs of a function of several variables

1 Answers1

Linked