anonymous unbound functions in python

Question

I would like to do something like the following:

def add(a, b):
    #some code

def subtract(a, b):
    #some code

operations = [add, subtract]
operations[0]( 5,3)
operations[1](5,3)

In python, is it possible to assign something like a function pointer?

Answer 1

Did you try it? What you wrote works exactly as written. Functions are first-class objects in Python.

Answer 2

Python has nothing called pointers, but your code works as written. Function are first-class objects, assigned to names, and used as any other value.

You can use this to implement a Strategy pattern, for example:

def the_simple_way(a, b):
    # blah blah

def the_complicated_way(a, b):
    # blah blah

def foo(way):
    if way == 'complicated':
        doit = the_complicated_way
    else:
        doit = the_simple_way

    doit(a, b)

Or a lookup table:

def do_add(a, b):
    return a+b

def do_sub(a, b):
    return a-b

handlers = {
    'add': do_add,
    'sub': do_sub,
}

print handlers[op](a, b)

You can even grab a method bound to an object:

o = MyObject()
f = o.method
f(1, 2) # same as o.method(1, 2)

Answer 3

Just a quick note that most Python operators already have an equivalent function in the operator module.