Python function as a function argument?

Question

Can a Python function be an argument of another function?

Yes.

def myfunc(anotherfunc, extraArgs):
    anotherfunc(*extraArgs)

To be more specific ... with various arguments ...

>>> def x(a,b):
...     print "param 1 %s param 2 %s"%(a,b)
...
>>> def y(z,t):
...     z(*t)
...
>>> y(x,("hello","manuel"))
param 1 hello param 2 manuel
>>>

Here's another way using *args (and also optionally), **kwargs:

def a(x, y):
  print x, y

def b(other, function, *args, **kwargs):
  function(*args, **kwargs)
  print other

b('world', a, 'hello', 'dude')

Output

hello dude
world

Note that function, *args, **kwargs have to be in that order and have to be the last arguments to the function calling the function.

Functions in Python are first-class objects. But your function definition is a bit off.

def myfunc(anotherfunc, extraArgs, extraKwArgs):
  return anotherfunc(*extraArgs, **extraKwArgs)

Sure, that is why python implements the following methods where the first parameter is a function:

• map(function, iterable, ...) - Apply function to every item of iterable and return a list of the results.
• filter(function, iterable) - Construct a list from those elements of iterable for which function returns true.
• reduce(function, iterable[,initializer]) - Apply function of two arguments cumulatively to the items of iterable, from left to right, so as to reduce the iterable to a single value.
• lambdas

Function inside function: we can use the function as parameter too..

In other words, we can say an output of a function is also a reference for an object, see below how the output of inner function is referencing to the outside function like below..

def out_func(a):

  def in_func(b):
       print(a + b + b + 3)
  return in_func

obj = out_func(1)
print(obj(5))

the result will be.. 14

Hope this helps.

1. Yes, it's allowed.
2. You use the function as you would any other: anotherfunc(*extraArgs)

1. Yes. By including the function call in your input argument/s, you can call two (or more) functions at once.

For example:

def anotherfunc(inputarg1, inputarg2):
    pass
def myfunc(func = anotherfunc):
    print func

When you call myfunc, you do this:

myfunc(anotherfunc(inputarg1, inputarg2))

This will print the return value of anotherfunc.

Hope this helps!