Changing text appearance of a part of a xticks string

Question

import pandas as pd
import matplotlib.pyplot as plt

def xtick_labels(time_range):
        labels = [
        i.strftime("%H:%M\n%Y-%m-%d")
        if (i.strftime("%H:%M:%S") == "00:00:00")
        else i.strftime("%H:%M")
        for i in time_range
    ]
        return labels


fig, ax = plt.subplots(figsize=(20, 4))
time_range = pd.date_range('01.01.2020 00:00:00', '01.03.2020 01:00:00', freq='2H')
ax.plot(time_range, len(time_range)*[1])
labels = xtick_labels(time_range)
ax.set_xticks(time_range, labels);

Is it possible to only change the appereance of a part of the dates in that xticks? Like changing the colour, different size? So not changing the entire xtick.

I know that changing the entire xtick is possible with:

ax.get_xticklabels()[-1].set_fontsize(14)
ax.get_xticklabels()[-1].set_color('red')

Maybe you can adapt this answer to your needs? https://stackoverflow.com/a/49041502/8310295 — K.Cl, Aug 20 '23 at 16:50
Or https://stackoverflow.com/questions/11325765/matplotlib-multiple-colours-in-tick-labels — JohanC, Aug 20 '23 at 17:00

score 1 · Accepted Answer · answered Aug 20 '23 at 17:24

It may be possible, but I think an easier approach would be to use custom annotations, instead of making the ticks do two separate things at once.

In this modified code, I store the location and text for the dates you want in red. Then, I loop through these locations and text values and annotate them onto the figure, using ax.annotate which I think is a better fit for what you are trying to accomplish:

import pandas as pd
import matplotlib.pyplot as plt

def annotations(time_range):
    data = []
    annotations = []
    for i in time_range:
        # If we want a custom tick, store it's data point and annotation
        if (i.strftime("%H:%M:%S") == "00:00:00"):
            data.append(i)
            annotations.append(i.strftime("%Y-%m-%d"))
    return data, annotations

fig, ax = plt.subplots(figsize=(20, 4))
time_range = pd.date_range('01.01.2020 00:00:00', '01.03.2020 01:00:00', freq='2H')
ax.plot(time_range, len(time_range)*[1])
labels = [i.strftime("%H:%M") for i in time_range]
ax.set_xticks(time_range, labels)

location, annnotations = annotations(time_range)
for x_loc, ann in zip(location, annnotations):
    y_loc = .93
    ax.annotate(
        text=ann,              # The text we are appending to the figure
        xy=(x_loc, y_loc),     # The (x,y) coordinates of that text in the axes DATA coordinates
        annotation_clip=False, # Tell MPL to not clip annotations outside of the axes range
        color='red', 
        fontsize=14, 
        ha='center',
        va='center'
    )

This produces what you want, and I think is clearer than trying to do some intense tick label customization. Notice that I hard-coded y_loc to be 0.93, which corresponds to the value of .93 on your y-axis where I wanted the annotations to be. You could probably automate this by getting the lower y limit of your axis and subtracting some constant value, but I did not do this for simplicity.

Changing text appearance of a part of a xticks string

1 Answers1