logscale = True 
    
# create test data
nPoints = 200
xValues = np.logspace(-14, -4, nPoints)
yValues = [x / (1.0e-9 + x) for x in xValues]

# set up figure
f, ax1 = plt.subplots(1)

# plot data       
ax1.plot(xValues, yValues)

# set range and scale
ax1.set_xlim(1.0e-14, 1.0e-4)
if (logscale):
    ax1.set_xscale('log')
ax1.set_ylim(-0.03, 1.03)

# save to file using pdf backend
f.savefig('minimal.pdf')