Python----面向对象---断言-assert

断言assert

 1 info = {}
 2 info['name'] = 'alex'
 3 # info['age'] = 18
 4 
 5 if 'name' not in info:
 6     raise KeyError('必须有name这个key')
 7 if 'age' not in info:
 8     raise KeyError('必须有age这个key')
 9 
10 结果为：
11 
12 Traceback (most recent call last):
13   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>
14     raise KeyError('必须有age这个key')
15 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：

 1 info = {}
 2 info['name'] = 'alex'
 3 # info['age'] = 18
 4 
 5 # if 'name' not in info:
 6 #     raise KeyError('必须有name这个key')
 7 # if 'age' not in info:
 8 #     raise KeyError('必须有age这个key')
 9 
10 assert ('name' in info) and ('age' in info)
11 
12 结果为：
13 
14 Traceback (most recent call last):
15   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>
16     assert ('name' in info) and ('age' in info)
17 AssertionError

断言报错，

 1 info = {}
 2 info['name'] = 'alex'
 3 info['age'] = 18
 4 
 5 # if 'name' not in info:
 6 #     raise KeyError('必须有name这个key')
 7 # if 'age' not in info:
 8 #     raise KeyError('必须有age这个key')
 9 
10 assert ('name' in info) and ('age' in info)
11 
12 if info['name'] == 'alex' and info['age'] > 10:
13     print('welcome')
14 
15 结果为：
16 
17 welcome

if 语句的执行依赖于前面代码执行结果