How to catch 404 error in urllib.urlretrieve

Question

Background: I am using urllib.urlretrieve, as opposed to any other function in the urllib* modules, because of the hook function support (see reporthook below) .. which is used to display a textual progress bar. This is Python >=2.6.

>>> urllib.urlretrieve(url[, filename[, reporthook[, data]]]) 

However, urlretrieve is so dumb that it leaves no way to detect the status of the HTTP request (eg: was it 404 or 200?).

>>> fn, h = urllib.urlretrieve('http://google.com/foo/bar') >>> h.items()  [('date', 'Thu, 20 Aug 2009 20:07:40 GMT'),  ('expires', '-1'),  ('content-type', 'text/html; charset=ISO-8859-1'),  ('server', 'gws'),  ('cache-control', 'private, max-age=0')] >>> h.status '' >>> 

What is the best known way to download a remote HTTP file with hook-like support (to show progress bar) and a decent HTTP error handling?

Answer 1

Check out urllib.urlretrieve's complete code:

def urlretrieve(url, filename=None, reporthook=None, data=None):   global _urlopener   if not _urlopener:     _urlopener = FancyURLopener()   return _urlopener.retrieve(url, filename, reporthook, data) 

In other words, you can use urllib.FancyURLopener (it's part of the public urllib API). You can override http_error_default to detect 404s:

class MyURLopener(urllib.FancyURLopener):   def http_error_default(self, url, fp, errcode, errmsg, headers):     # handle errors the way you'd like to  fn, h = MyURLopener().retrieve(url, reporthook=my_report_hook)