Well, there are two distinct features of IntelliSense as you know it.
One is auto-completion and the other is contextual help.

Auto-completion is included almost all beefy Python IDE's.

Contextual help is included even in IDLE, where if you begin typing a
function call, its docstring pops up around where you are typing.
Since many functions have dynamic arguments, I think this really is the
best solution, since the implementor of the function knows what would
be the most helpful to show.  Open the interactive IDLE prompt and type
max(, iter(, help(, for example -- although most of those are pretty
minimal.