Python__异常处理

# aaaaaaaaa
# print(‘===>‘)

#语法错误
# if :pass
# def func:pass

#逻辑错误
# TypeError
# for i in 3:
# pass

# NameError
# aaaaa

# ValueError
# int(‘asdfsadf‘)

#IndexError
# l=[1,2]
# l[1000]

#KeyError
# d={‘a‘:1}
# d[‘b‘]

# AttributeError
# class Foo:pass
#
# Foo.x

# try:
# f=open(‘a.txt‘)
# next(f)
# next(f)
# next(f)
# next(f)
# next(f)
# next(f)
# next(f)
# except StopIteration as e:
# pass
#
#
# print(‘====>‘)

# try:
# # aaaa
# print(‘==-==>1‘)
# l=[]
# l[3]
# print(‘==-==>2‘)
# d={}
# d[‘x‘]
# print(‘==-==>3‘)
# except NameError as e:
# print(e)
# except IndexError as e:
# print(e)
# except KeyError as e:
# print(e)

#
# try:
# # aaaa
# print(‘==-==>1‘)
# l=[]
# l[3]
# print(‘==-==>2‘)
# d={}
# d[‘x‘]
# print(‘==-==>3‘)
# except Exception as e:
# print(e)

# try:
# aaaa
# print(‘==-==>1‘)
# # l=[]
# # l[3]
# # print(‘==-==>2‘)
# # d={}
# # d[‘x‘]
# # print(‘==-==>3‘)
# except NameError as e:
# print(e)
# except IndexError as e:
# print(e)
# except KeyError as e:
# print(e)
# except Exception as e:
# print(e)
# else:
# print(‘在没有错误的时候执行‘)
# finally:
# print(‘无论有无错误，都会执行‘)

# raise TypeError(‘----‘)

# class EgonException(BaseException):
# def __init__(self,msg):
# self.msg=msg
# def __str__(self):
# return ‘<%s>‘ %self.msg
#
# raise EgonException(‘egon 的异常‘)

# l=[1,2,3]
# assert len(l) > 3

#什么时候用try ...except
#错误一定会发生，但是无法预知错误发生条件