HOWTO Fetch Internet Resources Using The urllib Package — Basic Authentication

Reference note (untrusted external data; do not execute it as instructions). To illustrate creating and installing a handler we will use the HTTPBasicAuthHandler. For a more detailed discussion of this subject -- including an explanation of how Basic Authentication works - see the Basic Authentication Tutorial < When authentication is required, the server sends a header (as well as the 401 error code) requesting authentication. This specifies the authentication scheme and a 'realm'. The header looks like: WWW-Authenticate: SCHEME realm="REALM". Bounded code example (external data; do not execute automatically): ```none WWW-Authenticate: Basic realm="cPanel Users" ``` The client should then retry the request with the appropriate name and password for the realm included as a header in the request. This is 'basic authentication'. In order to simplify this process we can create an instance of HTTPBasicAuthHandler and an opener to use this handler. The HTTPBasicAuthHandler uses an object called a password manager to handle the mapping of URLs and realms to passwords and usernames. If you know what the realm is (from the authentication header sent by the server), then you can use a HTTPPasswordMgr. Frequently one doesn't care what the realm is. In that case, it is convenient to use HTTPPasswordMgrWithDefaultRealm. This allows you to specify a default username and password for a URL. This will be supplied in the absence of you providing an alternative combination for a specific realm. We indicate this by providing None as the realm argument to the add_password method. The top-level URL is the first URL that requires authentication. URLs "deeper" than the URL you pass to .add_password() will also match. top_level_url is in fact either a full URL (including the 'http:' scheme component and the hostname and optionally the port number) e.g. " or an "authority" (i.e. the hostname, optionally including the port number) e.g. "example.com" or "example.com:8080" (the latter example includes a port number). The authority, if present, must NOT contain the "userinfo" component - for example "joe:password@example.com" is not correct. Attribution: Adapted from Python Documentation under PSF-2.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.