How to pass predefined arguments when storing a function

Question

Is it possible to store a function with predefined arguments to be called by another function?

For example:

def function(num):
    print num

trigger=fun         


        

Answer 1

You're looking for functools.partial:

>>> import functools
>>> def foo(number):
...     print number
... 
>>> bar = functools.partial(foo, 1)
>>> bar()
1

Answer 2

Someone already mentioned functools.partial which is preferred, but you can also use lambda functions without arguments:

trigger1 = lambda: function(1)
trigger2 = lambda: function(2)

Note: As someone mentioned, be careful about defining functions like this in loops or by referencing any value in the lambda body that might change.

You might end up in a situation like this:

a = []
for i in range(5):
    a.append(lambda: i)

b = [func() for func in a]
# equals [4, 4, 4, 4, 4]

# to avoid this, do a.append(lambda i=i: i)