python3异常处理和断言assert使用小结

异常处理

try:
    # 代码逻辑,只要其中任意一行报错都会被捕捉
    i = int('aaa')
    print(i)
except Exception as e:  # 如果出错执行
    # 捕捉错误
    print(e)  # invalid literal for int() with base 10: 'aaa'
else:
    print('no Error')  # 当没有错误的时候才执行
finally:  # 不管出不出错一定会执行
    print('over')

这里的Exception是一个包容所有错误的类，当然也可以写一些分类

try:
    s = 'aaa'
    print(s[5])
except IndexError as e:
    print(e)  # string index out of range
except IOError as e:
    print(e)

另外一种写法

try:
    s = aaa
    print(s[5])
except (IndexError, NameError) as e:
    print(e)  # name 'aaa' is not defined

主动触发异常

try:
    raise Exception('自首')
except Exception as e:
    print(e)  # 自首

自定义主动触发错误

class MyError(Exception):
    def __init__(self, msg):
        self.message = msg

    def __str__(self):
        return self.message
try:
    raise MyError('我错了')
except MyError as e:
    print(e)  # 我错了

assert 断言

print(123)
assert 1 == 1  # assert 条件，满足就执行下去，不满足报错
print(456)
print(123)
assert False  # AssertionError
print(456)

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作者：Tyran_U
来源：CSDN
原文：https://blog.csdn.net/tyrantu1989/article/details/78521298