Can't override matplotlibrc ?

It seems that I can't completely override my choice of

    > backend. E.g., I have set TkAgg as my default back end.
    > Yet if I modify examples/anim.py to include
    > matplotlib.use('GTKAgg') or matplotlib.use('GTK') it will
    > not run. A window appears, but it contains a static,
    > non-changing graph. To run anim.py, I have to modify
    > matplotlibrc. Same behavior the other way: with GTKAgg
    > selected in matplotlibrc, I can't run Todd's anim_tk.py,
    > even with TkAgg selected in the script. Am I doing
    > something stupid?

It works as expected for me, both ways. I can put TkAgg in my rc and
then matplotlib.use('GTKAgg') in anim.py and it works. Ditto the
other way around. Any chance you are working in an IDE? These changes
occur at module load time, and in an IDE such as IDLE, matplotlib will
only be loaded once.

JDH