Main axis are not shown when using grid
问题 I want to plot two graphs into the same figure with two different y-axis. In addition to it, I would like to add a grid and then save the plot as pdf. My problem is that - while the grid is drawn correctly - the main axis are not shown anymore. How can they be plotted as well? I am using matplotlib 1.5.1 and Python 2.7.11 . Here is the plot: And here is the code I am using: import matplotlib.pyplot as plt import numpy as np from matplotlib.backends.backend_pdf import PdfPages pp = PdfPages(