from matplotlib import pyplot as plt
from matplotlib.ticker import FormatStrFormatter
axes = plt.subplot(111)
axes.loglog([3, 4, 7], [2, 3, 4])
axes.xaxis.set_minor_formatter(FormatStrFormatter('%.2f'))
plt.xlim(1.8, 9.2)
plt.show()
Matplotlib: show labels for minor ticks also