pyqt provides python
wrappers for the Qt widgets library and is required by
the matplotlib Qt5Agg and Qt4Agg backends. Widely used on linux
and windows; many linux distributions package this as
'python-qt5' or 'python-qt4'.
Tk is a graphical user interface for Tcl
and many other dynamic languages. It can produce rich, native
applications that run unchanged across Windows, Mac OS X, Linux
and more.
wxpython provides python wrappers
for the wxWidgets library for use with the WX and WXAgg
backends. Widely used on linux, OS-X and windows, it is often
packaged by linux distributions as 'python-wxgtk'
WX is cross-platform GUI and
tools library for GTK, MS Windows, and MacOS. It uses native
widgets for each operating system, so applications will have the
look-and-feel that users on that operating system expect.