python学习笔记7-异常处理

1 写弄成了读

1 try:
    fh = open("testfile", "r")
    fh.write("This is my test file for exception handling!!")
 except IOError:
    print ("Error: can\'t find file or read data")

 else:
    print ("Written content in the file successfully")
 Error: can't find file or read data

2 异常触发

 #异常触发
 def functionName( level ):
    if level < 1:
       raise "Invalid level!", level
       # The code below to this would not be executed
       # if we raise the exception

3 自定义异常

 #自定义异常
 class Networkerror(RuntimeError):
    def __init__(self, arg):
       self.args = arg

 try:
    raise Networkerror("Bad hostname")
 except Networkerror,e:
    print e.args