Python----面向对象---断言-assert

断言assert

info = {}
info['name'] = 'alex'
# info['age'] = 18

if 'name' not in info:
    raise KeyError('必须有name这个key')
if 'age' not in info:
    raise KeyError('必须有age这个key')

结果为：

Traceback (most recent call last):
  File "C:/Users/xu516/PycharmProjects/Python全栈开发/第三模块/面向对象编程/33 try...except详细用法.py", line 68, in <module>
    raise KeyError('必须有age这个key')
KeyError: '必须有age这个key'

断言是断定会有什么，没有的话就会报错，可以用assert方法来实现，如下：

info = {}
info['name'] = 'alex'
# info['age'] = 18

# if 'name' not in info:
#     raise KeyError('必须有name这个key')
# if 'age' not in info:
#     raise KeyError('必须有age这个key')

assert ('name' in info) and ('age' in info)

结果为：

Traceback (most recent call last):
  File "C:/Users/xu516/PycharmProjects/Python全栈开发/第三模块/面向对象编程/33 try...except详细用法.py", line 70, in <module>
    assert ('name' in info) and ('age' in info)
AssertionError

断言报错，

info = {}
info['name'] = 'alex'
info['age'] = 18

# if 'name' not in info:
#     raise KeyError('必须有name这个key')
# if 'age' not in info:
#     raise KeyError('必须有age这个key')

assert ('name' in info) and ('age' in info)

if info['name'] == 'alex' and info['age'] > 10:
    print('welcome')

结果为：

welcome

if 语句的执行依赖于前面代码执行结果