wtf.py

class A(object):
    def hook(self, f):
        atime = 0
        def intime(*args):
            print atime
            atime += 1
            return f(*args)
        return intime

>>> f = A().hook(lambda b: b + 1)
>>> f(1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 5, in intime
UnboundLocalError: local variable 'atime' referenced before assignment
>>>

Thanks @sjl. it makes sense now. surprised I've never run in to this before.

@mattrobenolt came up with an alternate soltution: https://gist.github.com/mattrobenolt/6303154

here's the correct way to do it

class A(object):
    def hook(self, f):
        atime = []

        def intime(*args):
            print sum(atime)
            atime.append(1)
            return f(*args)
        return intime

f = A().hook(lambda b: b + 1)


for i in range(10):
    f(i)

and the python 3 way. bout time we start using it I think.

#!/usr/bin/env python3

class A(object):
    def hook(self, f):
        atime = 0
        def intime(*args):
            nonlocal atime
            print(atime)
            atime += 1
            return f(*args)
        return intime

f = A().hook(lambda b: b + 1)

# works as expected
for i in range(10):
    f(i)

and javascript for the fuck of it. and because someone once told me js and python had the same scope behavior.

a = function(f) {
    var a = 0;
    return function(i) {
        console.log(a);
        a = a+1;
        return f(i);
    }
}(function(x) { return x + 1 });

for (i = 0; i < 10; i += 1) {
  a(i);
}

Incidentally, when people complain about python not having proper closure support, this is (sometimes) what they mean.