Plot logarithmic axes with matplotlib in python

You can use the Axes.set_yscale method. That allows you to change the scale after the Axes object is created. That would also allow you to build a control to let the user pick the scale if you needed to.

The relevant line to add is:

ax.set_yscale('log')

You can use 'linear' to switch back to a linear scale. Here’s what your code would look like:

import pylab
import matplotlib.pyplot as plt
a = [pow(10, i) for i in range(10)]
fig = plt.figure()
ax = fig.add_subplot(2, 1, 1)

line, = ax.plot(a, color='blue', lw=2)

ax.set_yscale('log')

pylab.show()