How to set scientific notation on axis in matplotlib

Question

I am trying to plot a graph with two separate x-axis. One being some valve openning and the other the corresponding leak rate. I managed to make it work pretty well, though the format of that secondary axis doesn't always show scientific notations as seen on the figure down bellow Awful overlapping labels, see the upper axis How to force scientific notation display so that the labels wont overlap? Here is the script I am using:

#HEADERS
import numpy as np 
import matplotlib.pyplot as plt 
import matplotlib.ticker

from matplotlib import rc
rc('font', **{'family':'sans-serif','sans-serif':['Helvetica']})
rc('text', usetex=True)
#/HEADERS

turns = np.array([11.000, 11.500, 11.750, 12.000, 12.250, 12.375])
leak = np.array([3.89e-05, 4.63e-05, 1.67e-04, 1.45000000e-03, 8.61e-03, 1.71e-02])
pressure1 = np.array([7.9e-07, 3.0e-06, 3.5e-05, 6.1e-04, 5.1e-03, 1.8e-02])
pressure2 = np.array([8.22e-07, 8.22e-07, 8.71e-07, 1.8e-06, 1.150e-05, 7.24e-05])
pressure3 = np.array([2e-06, 2e-06, 2e-06, 1.2e-05, 1.2e-04, 6e-04])

fig = plt.figure(num='valve', figsize = (6.68, 6.68*1.3))
fig, ax1 = plt.subplots()
ax1.plot(turns, pressure1, 'r.', label= '$P_1$')
ax1.plot(turns, pressure2, 'b.', label= '$P_2$')
ax1.plot(turns, pressure3,'k.', label= '$P_3$')

plt.legend()

plt.minorticks_on()
plt.grid(b = True, which = 'major', axis = 'both')

ax1.errorbar(turns, pressure1, yerr = .4*pressure1, fmt='none', ecolor = 'k', elinewidth = 1, capsize = 1, label= '$P_{1err}$')
ax1.errorbar(turns, pressure2, yerr = .15*pressure2, fmt='none', ecolor = 'k', elinewidth = 1, capsize = 1, label= '$P_{2err}$')

plt.rc('text', usetex=True)
plt.rc('font', family='serif')

ax1.set_yscale('log', nonposy = 'mask')
ax1.set_ylabel(r'$P$')
ax1.set_xscale('linear')
ax1.set_xlabel('Opening (turns)')
plt.minorticks_on()
#plt.grid(b = True, which = 'major', axis = 'both')

#adding a secondary x-axis above
ax2 = ax1.twiny()
ax2.set_xlim(ax1.get_xlim())
new_tick_locations = turns
new_tick_label = leak #dtype here ?
ax2.set_xticks(new_tick_locations)
ax2.set_xticklabels(new_tick_label)
# I tried those commands from other threads but they all result in an error.
#ax2.xaxis.set_scientific(True)
#ax2.get_xaxis().set_major_formatter((matplotlib.ticker.Formatter(set_scientific(True)))
#ax2.get_xaxis().set_major_formatter().set_scientific(True)

ax2.set_xlabel(r'Leak rate (mbar$\times$L/s)')

plt.tight_layout()

#export png
plt.savefig(('export.png'), format = 'png', transparent=False, dpi = 300)
plt.show()

I'm using Python 3.6.

Thanks for your help.

Answer 1

Since you override the ticks, you can format them yourself and rotate them as well for more space:

new_tick_label = ['{:5.2e}'.format(x) for x in leak] 
ax2.set_xticks(new_tick_locations)
ax2.set_xticklabels(new_tick_label, rotation=30)

Result: