python function with arguments assigned to a variable

Question

I have a function

def x(whatever):
 ....

I want to assign

y = x(whatever)

So that I can pass around y to a wrapper which then calls the method that y refers to. The problem is that each type of function x can have variable arguments. Is it possible to do this in python, assigning y = x(whatever) and then pass around y as a parameter.

I tried y = x(whatever) and passed around y to the wrapper which then did

ret = y() # dict object is not callable

Thanks!

Answer 1

I think you are looking for functools.partial():

from functools import partial
y = partial(x, whatever)

When y is called, x(whatever) is called.

You can achieve the same with a lambda:

y = lambda: x(whatever)

but a partial() accepts additional arguments, which will be passed on to the wrapped callable.

• chepner: One other difference: the callable returned by partial fixes the argument to the value of whatever at that time. The callable returned by lambda uses the current value of whatever when it is called.
• Martijn Pieters: @chepner: That is true; the same applies to x. You can use lambda x=x, w=whatever: x(w) to bind both to the lambda.