Example of function returning a value or a generator, see stackoverflow.com/q/7113032/#comment42623885_7113061

gistfile1.py

>>> def foo(bar):
...     if bar:
...         def baz():
...             yield True
...         return baz()
...     else:
...         return False
... 
>>> foo(True)
<generator object baz at 0x100b82910>
>>> foo(False)
False