Why is i not incrementing in for loop?

Question

I'm new to programming may I know why my i is not incrementing in the for loop. I want to update the plot name for each subplot. Thank you.
Code screenshot

from matplotlib import pyplot as plt
fig= plt.figure()
fig,axes = plt.subplots(nrows=1, ncols=3,squeeze=False)
fig.tight_layout()

i=0
for current_ax in axes:
    current_ax[i].set_title(f"plot: {i}")
    i+=1

user_9214357 · Answer

You do not need to use current_axes[i], just current_axes.
Moreover, you could replace your for loop with this:

for i, current_ax in enumerate(axes, 0):
    current_ax.set_title(f'Plot: {i}')

user_10970343 · Answer

This is because your axes array is like shown below

[[
  
  ]]

so your array have only one plot with three objects in it. while you running your code the loop will only execute once. there is no problem with the counter increment. you can cross check this by printing i at the end of loop. so to make work this code in your way first pull out the first element from the array which will make the axes array with 3 objects ie 3 plots.

from matplotlib import pyplot as plt
fig= plt.figure()
fig,axes = plt.subplots(nrows=1, ncols=3,squeeze=False)
fig.tight_layout()
i=0
print('figarray1',axes)
axes=axes[0]
print('figarray2',axes)
for current_ax in axes:
    current_ax.set_title(f"plot: {i}")
    i+=1
    print(i)
plt.show()

output graph

Terminal Output

figarray1 [[
  
  ]]
figarray2 [
 
 ]
1
2
3

user_12649786 · Answer

I would recommend using enumerate here, as it is considered more Pythonic than indexing.

Below is how you would set both the titles and axes:

import matplotlib.pyplot as plt

fig = plt.figure()
fig, axes = plt.subplots(nrows=1, ncols=3, squeeze=False)
fig.tight_layout()

# enumerate titles for each plot (blue boxes in output below)   
for i, ax in enumerate(axes.flat):
    ax.set_title(f'Title {i}')

# label x and y axis for each plot (red boxes in output below)
plt.setp(axes, xlabel='x axis label')
plt.setp(axes, ylabel='y axis label')

Why is i not incrementing in for loop?

3 Answers

Below is how you would set both the titles and axes:

Output: