How to change axis labels in matplotlib?

Question

I have the following piece of code which creates a simple plot with matplotlib (python 3.6.9, matplotlib 3.1.2, Mac Mojave):

import numpy as np
import matplotlib.pyplot as plt

plt.imshow(np.random.random((50,50)))
plt.show()

The created plot is as expected:

Now, in order to relabel the xtick/ytick labels I am using the following code

import numpy as np
import matplotlib.pyplot as plt

plt.imshow(np.random.random((50,50)));

ticks, labels = plt.xticks()
labels[1] = '22'
plt.xticks(ticks, labels)

plt.show()

where I expect the second label to be replaced by '22', but everything else stays the same. However, I get the following plot instead:

1. There is some unexpected white area in the left part of the plot
2. All the other labels have vanished.

How to do it correctly?

Just as a reminder: I want to get the exact same result as the original image (first plot), ONLY with one of the lables changed.

This question has been asked before, one example is here. But the answer does not seem to work. Here is the code

import numpy as np
import matplotlib.pyplot as plt

fig, ax = plt.subplots()
plt.imshow(np.random.random((50,50)))

labels = [item.get_text() for item in ax.get_xticklabels()]
labels[1] = 'Test'
ax.set_xticklabels(labels)

plt.show()

which creates an image as follows:

which does not show the white area anymore, but still the other labels are not shown.

Answer 1

Create axes using subplots, so that you can have set_xticklabels method, so you can update the labels.

You need to use, canvas.draw() to get the values.

import numpy as np
import matplotlib.pyplot as plt

fig,ax = plt.subplots()
ax.imshow(np.random.random((50,50)));
fig.canvas.draw()
#labels = ['-10','0','22','20','30','40'] or
labels[2]=22
ax.set_xticklabels(labels)

plt.show()

Output:

Hope this is what you need!