一：函数作为返回值

>>> def lazy_sum(*args):
...     def sum():
...         ax = 0
...         for n in args:
...             ax = ax + n
...         return ax
...     return sum
...
>>> f=lazy_sum(1,2,3,4,5)
>>>
>>> f
<function sum at 0x7fd1b3eccaa0>
>>> f()
15
>>> f1=lazy_sum(1,2,3,4,5)
>>> f1()
15
>>> 

二：闭包

>>> def count():
...     fs=[]
...     for i in range(1,4):
...         def f():
...             return i*i
...         fs.append(f)
...     return fs
...
>>> f1, f2, f3 = count()
>>> f1
<function f at 0x7fd1b3edfed8>
>>> f1()
9
>>> f2()
9
>>> f3()
9
>>>