gistfile1.txt

In [16]: def counter_factory():
   ....:     count = [0]
   ....:     def _counter():
   ....:         count[0] += 1
   ....:         return count[0]
   ....:     return _counter
   ....: 

In [17]: f = counter_factory()

In [18]: g = counter_factory()

In [19]: f()
Out[19]: 1

In [20]: g()
Out[20]: 1

In [21]: f()
Out[21]: 2

In [22]: f()
Out[22]: 3