I forget everything all the time.

I have found a great solution for this, but it is not an IDE(!)

It is the bpython CLI. (I hear ipython is good too)

When I forget some string method's name, I just type "str." and a dialog box appears with all the options. If I am learning a new module I use "help(<function>)" or "<function>.__doc__"

oh yeah, and there is auto-complete. and syntax highlighting.