Django Gotchas: Django’s request.GET dictionary and ‘in’

I wish I’d known this a long time ago.  Django’s request object includes a dictionary of key/value pairs passed into the request via POST or GET methods.  That dictionary, however, works in a counter-intuitive fashion.  If a URL reads http://foo.com?a=boo, then the expected content of request.GET['a'] would be 'boo', right?  And most of us who’ve used other URL parsers in the past know that http://foo.com?a=boo&a=hoo know that the expected content of request.GET['a'] would be ['boo', 'hoo'].

Except it isn’t.  It’s just 'hoo'.  Digging into the source code, I learn that in Django’s MultiValueDict, __getitem__(self, key) has been redefined to return the last item of the list.  I have no idea why.  Maybe they wanted to ensure that a scalar was always returned.  The way to get the whole list (necessary when doing an ‘in’ request) is to call request.GET.getlist('a').

Lesson learned, an hour wasted.

This entry was automatically cross-posted from Elf's technical journal, ElfSternberg.com