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='')