Pass default variables to matplotlib

Question

I am creating some functions to create quality figures of a standard form using matplotlib. I typically create line plots, contour plots, etc. Is there a way to pass parameters (axis limits, tick locations, etc.) to matplotlib that instructs matplotlib to use the default values of the parameters? For example

I create a class

class my_class(object):
    xlimit = *something matplotlib reads as "use default"*
    ylimit = *something matplotlib reads as "use default"*
    linwidth = *something matplotlib reads as "use default"*

I create an instance of this class, but I only want to specify the xlimit

inst = myclass()
inst.xlimit = [0,1]

And I leave the ylimit unchanged, so matplotlib treats it as default.

I then have a function

def plot_func(x,y,fig,inst):

    ax = fig.gca()
    ax.set_xlim(inst.xlimit)
    ax.set_ylim(inst.ylimit)
    ax.plot(x,y,linewidth=inst.linwidth)

    return fig

Which I can call and pass my class instance. So far this is working for me just fine, but I have to set values for all my plotting parameters in my_class().

Is there a way to set these values in my_class() to something, so that if I decide I just want matplotlib's default calculations for things like limits, ticks, labels, etc. I can still pass these 'variables' to my function plot_func() where they will all be set and I can customize what I want, and leave everything else as default?

Just to avoid these answers, I am aware of matplotlib's rc settings, this is not what I am looking for.

Answer 1

Since almost all things in matplotlib are set by kwargs, you could define all your possible optional settings as None, unless you are going to set them manually.

Then, when you call ax.plot or ax.set_xlim, you can pass in your optional setting, so if the function receives the null value you get the default setting, otherwise you get your manually defined option.

class my_class(object):
    xlimit = (None, None)
    ylimit = (None, None)
    linewidth = None
    color = None


def plot_func(x,y,fig,inst):

    ax = fig.gca()
    ax.plot(x, y, linewidth=inst.linewidth, color=inst.color)
    ax.set_xlim(inst.xlimit)
    ax.set_ylim(inst.ylimit)

    return fig

Then, if we call this with the default settings, we get:

x = range(5)
y = range(5)

fig, ax = plt.subplots(1)
inst1 = my_class()
plot_func(x, y, fig, inst1)

fig.savefig('default_options.png')

Otherwise, we can change any settings we like:

ax.cla()

inst2 = my_class()
inst2.xlimit = [-2, 8]
inst2.linewidth = 5
inst2.color = 'r'

plot_func(x, y, fig, inst2)

fig.savefig('custom_options.png')