21.9. "urllib.error" — Exception classes raised by urllib.request
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**Source code:** Lib/urllib/error.py

======================================================================

The "urllib.error" module defines the exception classes for exceptions
raised by "urllib.request".  The base exception class is "URLError".

The following exceptions are raised by "urllib.error" as appropriate:

exception urllib.error.URLError

   The handlers raise this exception (or derived exceptions) when they
   run into a problem.  It is a subclass of "OSError".

   reason

      The reason for this error.  It can be a message string or
      another exception instance.

   Changed in version 3.3: "URLError" has been made a subclass of
   "OSError" instead of "IOError".

exception urllib.error.HTTPError

   Though being an exception (a subclass of "URLError"), an
   "HTTPError" can also function as a non-exceptional file-like return
   value (the same thing that "urlopen()" returns).  This is useful
   when handling exotic HTTP errors, such as requests for
   authentication.

   code

      An HTTP status code as defined in RFC 2616.  This numeric value
      corresponds to a value found in the dictionary of codes as found
      in "http.server.BaseHTTPRequestHandler.responses".

   reason

      This is usually a string explaining the reason for this error.

   headers

      The HTTP response headers for the HTTP request that caused the
      "HTTPError".

      New in version 3.4.

exception urllib.error.ContentTooShortError(msg, content)

   This exception is raised when the "urlretrieve()" function detects
   that the amount of the downloaded data is less than the expected
   amount (given by the *Content-Length* header).  The "content"
   attribute stores the downloaded (and supposedly truncated) data.
