Sympy Graphing: Usable Progress, Early Frustrations

Over the weekend, I did a bit of refactoring and added a couple of improvements to sympy/modules/graphing.py (where Fabian had laid a good foundation already). First, I've extended plot() to accept a list of functions in addition to a single function.

from sympy import Symbol
from sympy.modules.graphing import plot
x = Symbol('x')
plot([sqrt(x), log(x), sin(x)], xlabel="x label")


I also added in some code so that functions with discontinuities, such as sqrt where x < 0, are plotted correctly.

f_list = [sqrt(x), sqrt(-x), -sqrt(x), -sqrt(-x)]
plot(f_list, [x, -10.0, 10.0], title="Square Roots")


Unfortunately, this code has hit a snag getting through automated testing. At this point, my best hypothesis is that there is some incompatibility between py.test/doctest and the Tk backend for pylab. I'm going to try a different backend next. Ondrej has opened an issue here.