Question

I’m unable to write a custom urllib.FancyURLopener which initializes the user and passwd values in the constructor. I can get it to work fine with an empty constructor and a subsequent call to setpasswd. When I try to set the user and password in the constructor, I get strange errors regarding a missing attribute ‘tempcache’. Am I missing some Python syntax/usage regarding init?

I want to be able to specify my user and passwd in the constructor like so:

opener = MyRouterOpener("", "secretPassword")
page = opener.open("http://192.168.1.1/Status_Router.asp")
#do something with the page

Trying this way fails:

import urllib

class MyRouterOpener(urllib.FancyURLopener):
    def __init__(self, user, passwd):
        self.setpasswd(user, passwd)

    def setpasswd(self, user, passwd):
        self.__user = user
        self.__passwd = passwd

    def prompt_user_passwd(self, host, realm):
        return self.__user, self.__passwd

opener = MyRouterOpener("", "secretPassword")
statusPage = opener.open("http://192.168.1.1/Status_Router.asp")

Output:

Traceback (most recent call last):
  File "W:\Desktop\DynDns.enom.bad.py", line 15, in <module>
    statusPage = opener.open("http://192.168.1.1/Status_Router.asp")
  File "C:\Users\pengt\Python26\lib\urllib.py", line 179, in open
    if self.tempcache and fullurl in self.tempcache:
AttributeError: RouterOpener instance has no attribute 'tempcache'
Exception AttributeError: "RouterOpener instance has no attribute 'tempcache'" in <bound method RouterOpener.__del__ of <__main__.RouterOpener instance at 0x022AB9E0>> ignored

I’ve also tried:

import urllib

class RouterOpener(urllib.FancyURLopener):
def __init__(self, user, passwd):
    self.__user = user
    self.__passwd = passwd

def prompt_user_passwd(self, host, realm):
    return self.__user, self.__passwd

opener = RouterOpener("", "secretPassword")
statusPage = opener.open("http://192.168.1.1/Status_Router.asp")

But this produces:

Traceback (most recent call last):
  File "W:\Desktop\DynDns.enom.bad.py", line 12, in <module>
    statusPage = opener.open("http://192.168.1.1/Status_Router.asp")
  File "C:\Users\pengt\Python26\lib\urllib.py", line 179, in open
    if self.tempcache and fullurl in self.tempcache:
AttributeError: RouterOpener instance has no attribute 'tempcache'
Exception AttributeError: "RouterOpener instance has no attribute 'tempcache'" in <bound method RouterOpener.__del__ of <__main__.RouterOpener instance at 0x0231B968>> ignored

The only thing I’ve been able to get work is:

import urllib

class MyRouterOpener(urllib.FancyURLopener):
    def setpasswd(self, user, passwd):
        self.__user = user
        self.__passwd = passwd

    def prompt_user_passwd(self, host, realm):
        return self.__user, self.__passwd

opener = MyRouterOpener()
opener.setpasswd("", "secretPassword")
statusPage = opener.open("http://192.168.1.1/Status_Router.asp")

But then I’m specifying my user and passwd on a separate line. I know this is no big deal really, but like I say above I’m really wanting to know if I’m missing something about Python regarding inheritance and init etc.

Answer 1

You probably have to call the parent object’s init which sets the tempcache attribute.

def __init__(self, user, passwd):
    self.__user = user
    self.__passwd = passwd
    urllib.FancyURLopener.__init__(self)

(Call it with the proper arguments for the urllib.FancyURLopener creator)