Python: send arguments to function in dictionary

Question

Is it possible to pass arguments to a function within a dictionary?

d = {"A": foo(), "B": bar()}

def foo(arg):
    return arg + 1

def bar(arg):
    return arg - 1

In this case I want to pass arg to bar() by referencing the function dynamically

d["B"]  #<-- pass arg to bar()

Your dictionary syntax is wrong. The parens shouldn't be there. Otherwise you're actually calling the functions immediately and storing their return values. — tckmn
– tckmn, Commented Nov 20, 2015 at 22:44
@Doorknob - I wouldn't really call that a problem with syntax. It's perfectly valid Python; it just won't give the right result (and functions have to be defined before they're referenced and called, of course). — TigerhawkT3
– TigerhawkT3, Commented Nov 20, 2015 at 22:47
@TessellatingHeckler - The foo I'm looking at in the question doesn't do that. — TigerhawkT3
– TigerhawkT3, Commented Nov 20, 2015 at 22:58

TigerhawkT3 · Accepted Answer · 2015-11-20 22:50:04Z

2

It's possible, but you have to refer to the function (e.g. foo) without already calling it (e.g. foo()).

def foo(arg):
    return arg + 1

def bar(arg):
    return arg - 1

d = {"A": foo, "B": bar}

Result:

>>> d['A'](5)
6

edited Nov 20, 2015 at 22:50

answered Nov 20, 2015 at 22:45

TigerhawkT3

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2 Comments

Jonathon Reinhart Over a year ago

You should add that foo references the function named foo, whereas foo() (with parens) calls it.

TigerhawkT3 Over a year ago

I thought that was pretty clear since it was the only change in the code (other than eliminating the NameError), but hopefully the edit improves it.

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