assert expression

if not expression:
 raise AssertionError

if not expression:
 raise AssertionError(arguments)

> assert True   # 条件为 true 正常执行
> assert False  # 条件为 false 触发异常
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
AssertionError
> assert 1==1  # 条件为 true 正常执行
> assert 1==2  # 条件为 false 触发异常
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
AssertionError 
> assert 1==2, '1 不等于 2'
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
AssertionError: 1 不等于 2