In Matplotlib, I make dashed grid lines as follows:

fig = pylab.figure()    
ax = fig.add_subplot(1,1,1)
ax.yaxis.grid(color='gray', linestyle='dashed')

however, I can’t find out how (or even if it is possible) to make the grid lines be drawn behind other graph elements, such as bars. Changing the order of adding the grid versus adding other elements makes no difference.

Is it possible to make it so that the grid lines appear behind everything else?

According to this – http://matplotlib.1069221.n5.nabble.com/axis-elements-and-zorder-td5346.html – you can use Axis.set_axisbelow(True)

(I am currently installing matplotlib for the first time, so have no idea if that’s correct – I just found it by googling “matplotlib z order grid” – “z order” is typically used to describe this kind of thing (z being the axis “out of the page”))

To me, it was unclear how to apply andrew cooke’s answer, so this is a complete solution based on that:

ax.set_axisbelow(True)
ax.yaxis.grid(color='gray', linestyle='dashed')

If you want to validate the setting for all figures, you may set

plt.rc('axes', axisbelow=True)

or

plt.rcParams['axes.axisbelow'] = True

It works for Matplotlib>=2.0.

I had the same problem and the following worked:

[line.set_zorder(3) for line in ax.lines]
fig.show() # to update

Increase 3to a higher value if it does not work.