Exception
1.assertionerror举例
>>> my_list=['小甲鱼是帅哥']
>>> assert len(my_list)>0
>>> my_list.pop()
'小甲鱼是帅哥'
>>> assert len(my_list)>0
Traceback (most recent call last):
File "<pyshell#6>", line 1, in <module>
assert len(my_list)>0
AssertionError
>>>
2.attribute举例
>>> my_list.fishc #实际上my_list这个对象并没有fishc这样的属性,所以会报错
2 Traceback (most recent call last):
3 File "<pyshell#7>", line 1, in <module>
4 my_list.fishc
5 AttributeError: 'list' object has no attribute 'fishc'
3.indexerror举例
>>> my_list=[1,2,3]
>>> my_list[3]
3 Traceback (most recent call last):
4 File "<pyshell#9>", line 1, in <module>
5 my_list[3]
6 IndexError: list index out of range
4.keyerror举例
>>> my_dict={'one':1,'two':2,'three':3}
>>> my_dict['one']
1
>>> my_dict['four'] #访问的字典元素不存在
5 Traceback (most recent call last):
6 File "<pyshell#12>", line 1, in <module>
7 my_dict['four']
8 KeyError: 'four'
9 >>> my_dict.get('four') #使用get方法可以避免报错的出现,以避免让用户看到报错
5.nameerror举例
>>> fishc #尝试访问一个不存在的变量
2 Traceback (most recent call last):
3 File "<pyshell#14>", line 1, in <module>
4 fishc
5 NameError: name 'fishc' is not defined
6.typeerror举例(不同类型间的无效操作)
>>> 1+'' #‘1’
2 Traceback (most recent call last):
3 File "<pyshell#17>", line 1, in <module>
4 1+'1'
5 TypeError: unsupported operand type(s) for +: 'int' and 'str'
7.zerodivisionerror举例
>>> 5/0
2 Traceback (most recent call last):
3 File "<pyshell#18>", line 1, in <module>
4 5/0
5 ZeroDivisionError: division by zero
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1.try……except
try:
f=open('我为什么是一个文件.txt')
print(f.read())
f.close()
except OSError:
print('文件出错啦') #不会报错了,如果进入except就会打印出print('文件出错啦')的提示信息
如果开发人员还想看到报错那么完善为如下代码:
try:
f=open('我为什么是一个文件.txt')
print(f.read())
f.close()
except OSError as reason:
print('文件出错啦\n错误的原因是:'+str(reason))
捕获多个异常抛出except情况:
try:
sum=1+''
f=open('我为什么是一个文件.txt')
print(f.read())
f.close()
except OSError as reason:
print('文件出错啦\n错误的原因是:'+str(reason))
except TypeError as reason:
print('类型出错啦\n错误的原因是:'+str(reason))
——————————————————————————————————————————————————————————————
两个except可以优化为一个except如下:
except(OSError,TypeError):
print('出错啦')
except不明确error报错:
try:
sum=1+''
f=open('我为什么是一个文件.txt')
print(f.read())
f.close()
except: #except后未明确指出进入哪个错误
print('出错啦')
2.finally:无论如何都会被执行的代码
可以把上方f.close()代码写到finally中,try中不管有什么报错,那么close()语句都会被执行。
3.raise:自己引出一个异常
>>> raise
2 Traceback (most recent call last):
3 File "<pyshell#0>", line 1, in <module>
4 raise
5 RuntimeError: No active exception to reraise
>>> 1/0
7 Traceback (most recent call last):
8 File "<pyshell#1>", line 1, in <module>
9 1/0
10 ZeroDivisionError: division by zero
>>> raise ZeroDivisionError
12 Traceback (most recent call last):
13 File "<pyshell#2>", line 1, in <module>
14 raise ZeroDivisionError
15 ZeroDivisionError
>>> raise ZeroDivisionError('除数为零的异常')
17 Traceback (most recent call last):
18 File "<pyshell#3>", line 1, in <module>
19 raise ZeroDivisionError('除数为零的异常')
20 ZeroDivisionError: 除数为零的异常