25-Python3 错误和异常

25-Python3 错误和异常

'''

语法错误

'''

# while True print('hello,runoob')

'''

异常

'''

##ZeroDivisionError

# print(10*(1/0))

##NameError

# print(4+spam*3)

##TypeError

# print('2'+2)

'''

异常处理

'''

# while True:

#     try:

#         x = int(input('please enter a number:'))

#         break

#     except ValueError:

#         print('Oops!that was no valid number!try again')

# import sys,os

# fo_error = open('/Users/ligaijiang/PycharmProjects/foo_error.txt','w')

# fo_error.close()

#

# str_error = 'hello,runoob'

# n = 0

# d = 1

# for i in range(5):

#     print('第{0}行：{1}'.format(n,str_error))

#     n = n +1

#     d = d +1

# try:

#     f = open('/Users/ligaijiang/PycharmProjects/foo_error.txt')

#     s = f.readline()

#     i = int(s.strip())

# except OSError as err:

#     print('OS error:{}'.format(err))

# except ValueError:

#     print('Could not convert data to an integer')

# except:

#     print('Unexpected error:',sys.exc_info()[0])

#     raise

# import sys,os

#

# for arg in sys.argv[1:]:

#     try:

#         f = open(arg,'r')

#     except IOError:

#         print('cannot open',arg)

#     else:

#         print(arg,'has',len(f.readline()),'lines')

#         f.close()

# def this_fails():

#     x = 1/0

# try:

#     this_fails()

# except ZeroDivisionError as err:

#     print('Handling run-time error',err)

'''

抛出异常

'''

##使用raise语句抛出一个指定的异常

# raise NameError('HiThere')

##

# try:

#     raise NameError('HiThere')

# except NameError:

#     print('An exception flew by')

#     raise

'''

用户自定义异常

'''

# class MyError(Exception):

#     def __int__(self,value):

#         self.value = value

#     def __str__(self):

#         return repr(self.value)

# try:

#     raise MyError(2*2)

# except MyError as e:

#     print('My exception occurred,value:',e.value)

'''

定义清理行为

'''

#定义另无论在任何情况下都会执行的清理行为

# try:

#     raise KeyboardInterrupt

# finally:

#     print('Goodbye,world')

#

# def divide(x,y):

#     try:

#         result = x / y

#     except ZeroDivisionError:

#         print('division by zero!')

#     else:

#         print('result is',result)

#     finally:

#         print('executing finally clause')

#

# divide(2,1)

# divide(2,0)

# divide('2','1')

'''

预定义的清理行为

'''

fo_5 = open('/Users/ligaijiang/PycharmProjects/foo_5.txt','w')

fo_5.close()

s_5 = 'hello,runoob.'

n = 0

d = 1

for n in range(5):

    print('第{0}行：{1}'.format(d,s_5))

    n = n+1

    d = d+1

#没有关闭文件

# for line in open('/Users/ligaijiang/PycharmProjects/foo_5.txt'):

#     print(line,end='')

#会关闭文件

with open('/Users/ligaijiang/PycharmProjects/foo_5.txt') as f_5:

    for line in f_5:

        print(line,end='')