Plenty of great stuff here with obfuscation using leading underscores. Personally, I benefit greatly from the language design decision to make everything public as it reduces the time it takes to understand and use new modules.

However, if you're determined to implement private attributes/methods and you're willing to be unpythonic, you could do something along the lines of:

from pprint import pprint


# CamelCase because it 'acts' like a class
def SneakyCounter():

    class SneakyCounterInternal(object):

        def __init__(self):
            self.counter = 0

        def add_two(self):
            self.increment()
            self.increment()

        def increment(self):
            self.counter += 1

        def reset(self):
            print 'count prior to reset: {}'.format(self.counter)
            self.counter = 0

    sneaky_counter = SneakyCounterInternal()

    class SneakyCounterExternal(object):

        def add_two(self):
            sneaky_counter.add_two()

        def reset(self):
            sneaky_counter.reset()

    return SneakyCounterExternal()


# counter attribute is not accessible from out here
sneaky_counter = SneakyCounter()

sneaky_counter.add_two()
sneaky_counter.add_two()
sneaky_counter.reset()

# `increment` and `counter` not exposed (AFAIK)
pprint(dir(sneaky_counter))

Hard to imagine a case where you'd want to do this, but it is possible.

There is plenty of great stuff here with obfuscation using leading underscores. Personally, I benefit greatly from the language design decision to make everything public as it reduces the time it takes to understand and use new modules.

However, if you're determined to implement private attributes/methods and you're willing to be unpythonic, you could do something along the lines of:

from pprint import pprint


# CamelCase because it 'acts' like a class
def SneakyCounter():

    class SneakyCounterInternal(object):

        def __init__(self):
            self.counter = 0

        def add_two(self):
            self.increment()
            self.increment()

        def increment(self):
            self.counter += 1

        def reset(self):
            print 'count prior to reset: {}'.format(self.counter)
            self.counter = 0

    sneaky_counter = SneakyCounterInternal()

    class SneakyCounterExternal(object):

        def add_two(self):
            sneaky_counter.add_two()

        def reset(self):
            sneaky_counter.reset()

    return SneakyCounterExternal()


# counter attribute is not accessible from out here
sneaky_counter = SneakyCounter()

sneaky_counter.add_two()
sneaky_counter.add_two()
sneaky_counter.reset()

# `increment` and `counter` not exposed (AFAIK)
pprint(dir(sneaky_counter))

It is hard to imagine a case where you'd want to do this, but it is possible.