I just noted a strange behavior of contour(). When a contour plot is
created with negative values and using a single color instead of a cmap,
contour _always_ uses the contour.negative_linestyle, even if linestyles
are specifically provided:
x = linspace(-pi,pi,100)
X,Y = meshgrid(x,x)
Z = cos(X) + 0.5*cos(Y)
contour(X,Y,Z, colors='k', linestyles='solid')
I would expect the contour.negative_linestyle to be used when
linestyles=None, but not if it is explicitly specified. More serious,
even in the following case the effect takes place.
contour_ls = ['solid']*9
contour(X,Y,Z,10, colors='k', linestyles=contour_ls)
Should we consider this as a bug and fix it ???