request.POST["key"] returns only the last value of a list

[elcio@…]

If I submit a list of inputs with the same name (as a checkboxes list) or request something like http://myserver/path?key=a&key=b&key=c I get strange things:

print request.POST
print request.POST["key"]
print dict(request.POST)["key"]

results:

{'key': ['a', 'b', 'c']}
c
['a', 'b', 'c']

I think request.POSTkey should return the same as dict(request.POST)key. The same with GET. Am I missing something?

I'm using rev. [1785] and the built-in Django server.

[Simon Willison]

This is a feature, not a bug. If you want a list of values for a key, use the following:

values = request.POST.getlist('key')

The reasoning behind this is that an API method should consistently return either a string or a list, but never both. The common case in web applications is for a form key to be associated with a single value, so that's what the [] syntax does. getlist() is there for the occasions (like yours) when you intend to use a key multiple times for a single value.

[Simon Willison]

You can read more about this in the documentation comment at the top of the MultiValueDict class here: ​http://code.djangoproject.com/browser/django/trunk/django/utils/datastructures.py

I've opened ticket #1131 suggesting a repr method is added to MultiValueDict to make the special nature of the data structure more instantly clear.

[rjwittams]

I've got to say that I think MultiValueDict is more trouble than it is worth. It seems to just lead to misunderstandings, and it also makes the implementation more complex (all the "needs list" stuff for formfields).

[anonymous]

It would be tremendous, if getlist() would also accept an optional fallback parameter, like get() does.