Python inner functions

Question

In python, I can write :

def func():
    x = 1
    print x
    x+=1

    def _func():
        print x
    return _func

test = func()
test()

Answer 1

You can't rebind variables that are closed over in Python 2 (you can use nonlocal in Python 3). If I have to do what you're doing in Python 2 then I do the following workaround:

class Pointer(object):
    def __init__(self, val):
        self.val = val

def func():
    px = Pointer(1)
    print px.val
    px.val += 1

    def _func():
        print px.val
    return _func

test = func()
test()

Basically I put whatever values I need to be mutated onto an object - sometimes I use a list with one element - and then re-write the code so that all that happens is method calls. The above is actually equivalent to:

class Pointer(object):
    def __init__(self, val):
        self.val = val

def func():
    px = Pointer(1)
    print px.val
    px.__setattr__('val', px.val + 1)

    def _func():
        print px.val
    return _func

test = func()
test()