Configuring grid-lines

Consider the figure below.

This image has been set up with the following code.

  plt.rc('text', usetex=True)
  plt.rc('font', family='serif')
  fig, ax = plt.subplots()
  
  ax.set_xlabel("Run Number", fontsize=25)
  
  plt.grid(True, linestyle='--')
  plt.tick_params(labelsize=20)
  ax.set_xticklabels(map(str,range(number_of_runs)))
  ax.minorticks_on()

  ax.set_ylim([0.75,1.75])

I have not included the code that actually generates the data for plotting for the sake of clarity.

Unlike the diagram above, I would like to draw grid-lines perpendicular to the X-axis through each orange (and hence blue) dot. How do I do this? The x-coordinates of the successive orange and blue dots form the same arithmetic progression in my code.

Also I notice that the tick numbers numbered 1,2,... are wrong for my application. Instead, I would like each successive grid-line, which I ask for as perpendicular to the X-axis in the previous step, to be numbered sequentially from 1 along the X-axis. How do I configure the Xtick marks for this?

Solution

The grid lines cross the xticks (or yticks). You need to define xticks properly so that the grid lines cross your data points (the dots)

example below:

import matplotlib.pyplot as plt
fig, ax = plt.subplots()
number_of_runs = range(1,10)    # use your actual number_of_runs
ax.set_xticks(number_of_runs, minor=False)
ax.xaxis.grid(True, which='major')

In case you want to have only vertical lines, add this:

ax.yaxis.grid(False, which='major')