CODEWITHSUNDEEP
pythonfunction-pointers
t3rse
t3rse

Reputation: 10124

function pointers in python

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?

Upvotes: 10

Views: 17120

Answers (3)

Ignacio Vazquez-Abrams
Ignacio Vazquez-Abrams

Reputation: 799082

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

Upvotes: 1

Ned Batchelder
Ned Batchelder

Reputation: 375744

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)

Upvotes: 9

Joe Ganley
Joe Ganley

Reputation: 602

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

Upvotes: 29

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