Access functions within functions in python

Question

Given a function within a function, how do I call the inner function from an external function?

ex.

def a():
    print 'a'
    def b():
        print 'b'
        def c():
            print 'c'

def d():
    # how would I now call a, b and c from here?
    def e():
        # how would I call a, b and c from here as well?

Yes I know it's horrible code structure and should not be done - but how do you do it?

Edit: Any way to do this using decorators?

You can do it by using class instead of def. What on earth can your use case be? — John La Rooy
– John La Rooy, Commented Aug 20, 2012 at 5:25
@BurhanKhalid, it's not quite impossible, but certainly not something you should do — John La Rooy
– John La Rooy, Commented Aug 20, 2012 at 5:27

BrenBarn · Accepted Answer · 2012-08-20 05:25:31Z

8

You cannot. b and c are local variables inside a and do not exist except while a is executing.

(Since these are constants, you can technically access them via a.__code__.co_consts, but this is not a real solution even if you're okay with horrible code structure. You would have to execute the function with exec and you can't pass arguments to it.)

answered Aug 20, 2012 at 5:25

BrenBarn

253k39 gold badges421 silver badges392 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

behnam Over a year ago

And, this is indeed one of the techniques that are used to create absolute private attributes in Python.

Lauritz V. Thaulow Over a year ago

@behnam Can you give an example of where absolute private attributes is used in a python program? I'm curious as to why it's necessary, and the actual implementation.

Ignacio Vazquez-Abrams · Accepted Answer · 2012-08-20 05:25:22Z

3

You can't, since those functions are created when the outer function is called, and are destroyed when the outer function exits. You would need to put a reference to the inner function somewhere persistent if you wanted to access them from elsewhere.

answered Aug 20, 2012 at 5:25

Ignacio Vazquez-Abrams

804k160 gold badges1.4k silver badges1.4k bronze badges

2 Comments

kindall Over a year ago

You could, for example, return these references from the outer function.

DSM Over a year ago

I don't want to post this as an answer because no one should get karma for something so perverse, but the obvious place to stash the references is in the function itself.. adding b.c = c and a.b = b after the function declarations would enable a.b.c().. (shudder)

Matthew Adams · Accepted Answer · 2012-08-20 05:39:20Z

1

With this structure, you can only call a() in the two places you indicated. b() is only defined while a() runs, and c() is only defined while b() runs. a() can be called from anywhere since it defined globally.

For example:

def a():
    print 'a'
    def b():
        print 'b'
        def c():
            print 'c'

def d():
    # how would I now call a, b and c from here?
    a()
    def e():
        a()
        # how would I call a, b and c from here as well?

d()

results in

(Similarly, e() is only defined when d() is running. d(), like a(), is defined globally.)

edited Aug 20, 2012 at 5:39

answered Aug 20, 2012 at 5:32

Matthew Adams

10.3k3 gold badges31 silver badges43 bronze badges

Comments

beatt · Accepted Answer · 2012-08-20 11:06:54Z

0

You can change your outer function so it will return your inner function

answered Aug 20, 2012 at 11:06

beatt

961 silver badge7 bronze badges

Collectives™ on Stack Overflow

Access functions within functions in python

4 Answers 4

2 Comments

2 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

2 Comments

2 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related