1.异常的抛出
# encoding=UTF-8
class ShortInputException(Exception):
'''一个由用户定义的异常类'''
def __init__(self, length, atleast):
# 让这个自定义的异常继承于Exception类
Exception.__init__(self)
self.length = length
self.atleast = atleast
try:
text = input('Enter something --> ')
if len(text) < 3:
# 抛出异常
raise ShortInputException(len(text), 3)
# 其他工作能在此处继续正常运行
except EOFError:
print('Why did you do an EOF on me?')
except ShortInputException as ex:
print(('ShortInputException: The input was ' +
'{0} long, expected at least {1}')
.format(ex.length, ex.atleast))
else:
print('No exception was raised.')
2.异常的处理
try :
text = input('Enter something -->')
except EOFError:
print('EOF error')
except KeyboardInterrupt:
print('KeyboardInterrupt error')
else:
print('You entered {}'.format(text))3.异常的Finally
import sys
import time
f = None
try:
# 打开文件
f = open("poem.txt")
# 我们常用的文件阅读风格
while True:
# 开始读取文件
line = f.readline()
if len(line) == 0:
break
print(line, end='')
# 使得控制台中输出与的内容可以立马显示出来
sys.stdout.flush()
print("Press ctrl+c now")
# 为了确保它能运行一段时间
# time.sleep 函数任意在每打印一行后插入两秒休眠
time.sleep(2)
except IOError:
print("Could not find file poem.txt")
except KeyboardInterrupt:
print("!! You cancelled the reading from the file.")
finally:
if f:
# 关闭文件流
f.close()
print("(Cleaning up: Closed the file)")
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