Python中assert用来判断语句的真假，如果为假的话将触发AssertionError错误

如：

>>> a = 23
>>> a
23
>>> assert a == 23
>>> a -=1
>>> a
22
>>> assert a == 23

Traceback (most recent call last):
  File "", line 1, in
    assert a ==23
AssertionError
>>>

Python中assert的用法