PGF backend

Hello !

I would like to have some hints about the matplotlib usage, especially
the PGF/tikz backend.

I use a latex document, and almost only tikz figures.

I have a couple of problems with the matplotlib package.

The first is the preemptive behaviour of the matplotlib package over the
used fonts. I would like the text to be let "as it", without adding
stuff like \sffamily\ttffont, and so on.

For example, if I write "$L^2$" as a legend axis, I want this text to be
let "as it", without any modification by the pgf backend.

A second point, is that I would like to not use the
\begin{pgffigure}\end{pgffigure}, the \makeatletter and fancy stuff like
that. I want to take care myself of the latex code. Is it possible ?

Finally, Would it be possible to specify the size of the graphic
somewhere ? The documentation is rather vague about it.

Thank you for help.