Plotting to 1 figure using multiple functions with Matplotlib, Python

Question

I have a main program main.py in which I call various functions with the idea that each function plots something to 1 figure. ie all the function plots append detail to the 1 main plot.

Currently I have it set up as, for example:

main.py:

import matplotlib.pylab as plt    

a,b,c = 1,2,3

fig = func1(a,b,c)

d,e,f = 4,5,6

fig = func2(d,e,f)

plt.show()

func1:

def func1(a,b,c):
    import matplotlib.pylab as plt
    ## Do stuff with a,b and c ##
    fig = plt.figure()    
    plt.plot()
    return fig

func2:

def func2(d,e,f):
    import matplotlib.pylab as plt
    ## Do stuff with d,e and f ##
    fig = plt.figure()    
    plt.plot()
    return fig

This approach is halfway there but it plots separate figures for each function instead of overlaying them.

How can I obtain 1 figure with the results of all plots overlaid on top of each other?

Answer 1

It is much better to use the OO interface for this puprose. See http://matplotlib.org/faq/usage_faq.html#coding-styles

import matplotlib.pyplot as plt    

a = [1,2,3]
b = [3,2,1]

def func1(ax, x):
    ax.plot(x)

def func2(ax, x):
    ax.plot(x)

fig, ax = plt.subplots()
func1(ax, a)
func2(ax, b)

It seems silly for simple functions like this, but following this style will make things much much less painful when you want to do something more sophisticated.

Answer 2

This should work. Note that I only create one figure and use the pyplot interface to plot to it without ever explicitly obtaining a reference to the figure object.

import matplotlib.pyplot as plt    

a = [1,2,3]
b = [3,2,1]

def func1(x):
    plt.plot(x)

def func2(x):
    plt.plot(x)

fig = plt.figure()
func1(a)
func2(b)