How to call Python partial without using parentheses?

Question

Suppose the code below:

from functools import partial
import random

def integer(min=1, max=10):
    return random.randint(min, max)

def double(min=1, max=10):
    return random.uniform(min, max)

if __name__ == '__main__':
    p1 = partial(integer, 5, 10)
    p2 = partial(double, 5, 10)
    for f in [p1, p2]:
        f() # I'd like to know if there's a different way to call this like `call(f)` or something

As mentioned in the comment, I'd like to know if there's a way to call f without using parentheses. One step further, suppose I can call f without using parentheses, if I would like to pass additional parameters to f, how do I go about it (like call(f, additional_param_1, additional_param_2))?

Thank you in advance for your answers!

Why? Are you just playing with Python syntax, or do you have some concrete reason to do this? — Chris
– Chris, Commented Aug 7, 2019 at 1:33
There is f.__call__() but I doubt that's what you're after. Why do you want to be able to do call(f, arg1, arg2)? What problem are you really trying to solve, because there probably is a way that doesn't involve a call() function - although you could write such a function quite easily yourself. — Grismar
– Grismar, Commented Aug 7, 2019 at 1:41
@user1330974 no, there isn't. There used to be an apply function in Python 2, but even then it was considered obsolete probably decades ago. Why would you ever need this? — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Aug 7, 2019 at 2:10

Grismar · Accepted Answer · 2019-08-07 07:22:27Z

1

Not in base Python, but you can easily write call() yourself:

from functools import partial
import random

def integer(min=1, max=10):
    return random.randint(min, max)

def double(min=1, max=10):
    return random.uniform(min, max)

def call(f, *args, **kwargs):
    return f(*args, **kwargs)

if __name__ == '__main__':
    p1 = partial(integer, 5, 10)
    p2 = partial(double, 5, 10)
    for f in [p1, p2]:
        call(f)

Note: you have a typo in your example, you're calling partial on int, but your function is called integer. (neither is a very good name and I think you're trying to solve a problem that you're not stating, that has a better solution)

edited Aug 7, 2019 at 7:22

answered Aug 7, 2019 at 1:45

Grismar

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10 Comments

Aaron Over a year ago

I mean it makes no sense to do this in the first place, but might it be better to return the results of the function f from the call function as well?

juanpa.arrivillaga Over a year ago

@user1330974 they mean actually return the results, currently, call will always return None

Grismar Over a year ago

Added a return, but of course there's still all kinds of issues with generators, asynchronous functions, etc. It's really not something you should do, unless you have a very specific use for it. @user1330974 the 'clean' way of doing things is to follow convention - in Python, that means clearly calling a function when you need it, with parentheses. Cleaner doesn't always mean fewer symbols.

Grismar Over a year ago

@user1330974 again, calling the script with code like that is a massive anti-pattern and there's very little use for it that could not be achieved in safer and more efficient ways. You'd do well to learn to write the language as it was intended, instead of trying to subvert it in unreadable and unpredictable spaghetti code.

Aaron Over a year ago

@user1330974 You could use eval to execute functions like that, however allowing the user to execute arbitrary python is a big security risk, so it should not be done if anyone other than you is using the script. docs.python.org/3/library/functions.html#eval

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