Axis overlapping line in matplotlib

Question

I'm currently trying to draw a series of arbitrary lines on a matplotlib graph. Here is the code I'm using:

import matplotlib.pyplot as pyplot

def center_origin(axis):
    '''Center the axis in the middle of the picture'''
    axis.spines['right'].set_color('none')
    axis.spines['top'].set_color('none')
    axis.xaxis.set_ticks_position('bottom')
    axis.spines['bottom'].set_position(('data',0))
    axis.yaxis.set_ticks_position('left')
    axis.spines['left'].set_position(('data',0))

def render(lines):
    figure = pyplot.figure(figsize=(4,4))
    axis = figure.add_subplot(1, 1, 1)

    center_origin(axis)        

    for (x1, y1), (x2, y2) in lines:
        axis.add_line(pyplot.Line2D((x1, x2), (y1, y2), color='red'))

    axis.set_xlim(-1.2, 1.2)
    axis.set_ylim(-1.2, 1.2)
    return figure

if __name__ == '__main__':
    render([((1, 0), (0, 1)),
            ((1, 0), (-1, 0)),
            ((1, 0), (0, -1))]).show()
    raw_input('block > ')

It produces a graph that looks like this:

Currently, the x-axis is covering up the red line that should run from (1, 0) to (-1, 0). I tried placing the center_origin function to both before and after I drew the lines, but nothing changed.

How can I make matplotlib draw my lines over the axis?

Answer 1

The attribute zorder determines the order in which the lines are drawn on top of each other. Try pyplot.Line2D((x1, x2), (y1, y2), color='red', zorder = 1). Play around with the value, you may need something higher.