一、python assert的作用:
根据Python 官方文档解释(https://docs.python.org/3/reference/simple_stmts.html#assert), "Assert statements are a convenient way to insert debugging assertions into a program".
二、一般的用法是:
assert condition
用来让程序测试这个condition,如果condition为false,那么raise一个AssertionError出来。逻辑上等同于:
if not condition: raise AssertionError()
比如如下的例子:
>>> assert 1==1 >>> assert 1==0 Traceback (most recent call last): File "<pyshell#1>", line 1, in <module> assert 1==0 AssertionError >>> assert True >>> assert False Traceback (most recent call last): File "<pyshell#3>", line 1, in <module> assert False AssertionError >>> assert 3<2 Traceback (most recent call last): File "<pyshell#4>", line 1, in <module> assert 3<2 AssertionError
三、如何为assert断言语句添加异常参数
assert的异常参数,其实就是在断言表达式后添加字符串信息,用来解释断言并更好的知道是哪里出了问题。格式如下:
assert expression [, arguments]
assert 表达式 [, 参数]
比如如下的例子:
>>> assert len(lists) >=5,‘列表元素个数小于5‘
Traceback (most recent call last):
File "D:/Data/Python/helloworld/helloworld.py", line 1, in <module>
assert 2>=5,‘列表元素个数小于5‘
AssertionError: 列表元素个数小于5
>>> assert 2==1,‘2不等于1‘
Traceback (most recent call last):
File "D:/Data/Python/helloworld/helloworld.py", line 1, in <module>
assert 2==1,‘2不等于1‘
AssertionError: 2不等于1
--------------------------------------------------------------------
参考链接:
https://www.cnblogs.com/liuchunxiao83/p/5298016.html
https://www.cnblogs.com/cedrelaliu/p/5948567.html