Tkinter is Python's "default GUI framework". At least, that's what they continue to claim (https://wiki.python.org/moin/TkInter), and it's the GUI library I ran into first when I first learned Python.
How does it look and feel once you get started? Well, let's just say it's a bad sign if a GUI framework website has no screenshots. Even with increasingly hacky theming engines layered on top, it still is hard to get anything feeling close to native: http://tktable.sourceforge.net/tile/screenshots/macosx.html
Go ahead, you can start laughing...
(for anybody that is saddened by the above, there are thankfully binding libraries for Qt and Wx, both of which do get you fairly decent cross-platform widgets from within Python, and either of which would be better default GUI libraries in 2014.)