Setting `axes.linewidth` without changing the `rcParams` global dict

The above answer does not work, as it is explained in the comments. I suggest to use spines.

import matplotlib.pyplot as pltfig = plt.figure()ax = fig.add_subplot(111)# you can change each line separately, like:#ax.spines['right'].set_linewidth(0.5)# to change all, just write:for axis in ['top','bottom','left','right']:  ax.spines[axis].set_linewidth(0.5)plt.show()# see more about spines at:#http://matplotlib.org/api/spines_api.html#http://matplotlib.org/examples/pylab_examples/multiple_yaxis_with_spines.html

plt.setp(ax.spines.values(), linewidth=5)

Yes, there's an easy and clean way to do this.

Calling 'axhline' and 'axvline' from an axis instance appears to be the technique endorsed in the MPL Documentation.

In any event, it is simple and gives you fine-grained control over the appearance of the axes.

So for instance, this code will create a plot and color the x-axis green and increase the line width of the x-axis from a default value of "1" to a value of "4"; the y-axis is colored red and the line width of the y-axis is increased from "1" to "8".

from matplotlib import pyplot as PLTfig = PLT.figure()ax1 = fig.add_subplot(111)ax1.axhline(linewidth=4, color="g")        # inc. width of x-axis and color it greenax1.axvline(linewidth=4, color="r")        # inc. width of y-axis and color it redPLT.show()

The axhline/axvline function accepts additional arguments which ought to allow you do any pretty much whatever you want aesthetically, in particular any of the ~matplotlib.lines.Line2D properties are valid kwargs (e.g., 'alpha', 'linestyle', capstyle, joinstyle).