arrowed_spines.py

import matplotlib.pyplot as plt

def arrowed_spines(ax=None, arrow_length=20, labels=('', ''), arrowprops=None):
    xlabel, ylabel = labels
    if ax is None:
        ax = plt.gca()
    if arrowprops is None:
        arrowprops = dict(arrowstyle='<|-', facecolor='black')

    for i, spine in enumerate(['left', 'bottom']):
        # Set up the annotation parameters
        t = ax.spines[spine].get_transform()
        xy, xycoords = [1, 0], ('axes fraction', t)
        xytext, textcoords = [arrow_length, 0], ('offset points', t)
        ha, va = 'left', 'bottom'

        # If axis is reversed, draw the arrow the other way
        top, bottom = ax.spines[spine].axis.get_view_interval()
        if top < bottom:
            xy[0] = 0
            xytext[0] *= -1
            ha, va = 'right', 'top'

        if spine is 'bottom':
            xarrow = ax.annotate(xlabel, xy, xycoords=xycoords, xytext=xytext, 
                        textcoords=textcoords, ha=ha, va='center',
                        arrowprops=arrowprops)
        else:
            yarrow = ax.annotate(ylabel, xy[::-1], xycoords=xycoords[::-1], 
                        xytext=xytext[::-1], textcoords=textcoords[::-1], 
                        ha='center', va=va, arrowprops=arrowprops)
    return xarrow, yarrow