[Matplotlib-users] two axes

[Tommy C. <tom...@gm...>]

In gnuplot it is quite easy to create two axes, but I can't figure out
how to do it in matplotlib. I'm trying this:

import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt

for key1 in keys1:
    ax1.plot(x, y, style, label=label, color=color, linewidth=3)
    ax1.set_xlabel(xlabel)
    ax1.set_ylabel(ylabel1)
    ax2.set_ylabel(ylabel2)
    plt.legend(loc='lower right', shadow=True)
    plt.suptitle(title, fontsize=14, fontweight='bold')
    axes = plt.gca()
    axes.set_ylim([0,1])
    plt.grid(b=True, which='major', color='k', linestyle='--')
    plt.savefig('{}.png'.format(key1), dpi=600)
    plt.close()
    plt.clf()

But I get this error:
lib/python3.3/site-packages/matplotlib/axes.py:4749: UserWarning: No
labeled objects found. Use label='...' kwarg on individual plots.
  warnings.warn("No labeled objects found. "

What am I doing wrong? Thanks.