>>> def scope():
...     for x in range(1,10):
...             if x > 3:
...                     print(a)
...             else:
...                     a=x
...
>>> scope()
3
3
3
3
3
3
>>> print(a)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'a' is not defined