Bug summary

When I turn on "useMathText" in matplotlib in the intention to replace 1e6 by $\times 10^6$, the formatting of the commas in the tick labels themselves get wrong. Before they are correct in the form "3,5", with "useMathText" they become "3, 5", with (half?) a whitespace between the comma and the following digit.

Code for reproduction

%matplotlib inline
import locale
locale.setlocale(locale.LC_ALL, "deu_deu")
import matplotlib.pyplot as plt

plt.rcParams['axes.formatter.use_locale'] = True

fig, ax = plt.subplots()
x = [1000, 2000, 3000, 3.5e6]
y = [1, 4, 3, 5]
ax.plot(x, y, linestyle = "", marker = "o")
ax.set_xlabel("the x-axis")
ax.ticklabel_format(axis = 'x', useMathText = True)

Actual outcome

the formatting of the decimal power is altered, but the ticklabels themselves are rendered incorrectly (additional space between comma and following digit)

Expected outcome

the formatting of the decimal power is altered, and the ticklabels themselves are rendered correctly (as before adding useMathText = True)

Additional information

apparently, matplotlib uses LaTeX to render the mathematical notation of power, and also changes the way the normal ticklabels are created to TeX mode.
however, when using comma as decimal separator in TeX you have to consider that it is written by americans, using the comma as an element separator, not decimal separator, and therefore in standard configuration automatically adds a space behind the comma.

this can be fixed by using
3{,}5
or
3,\!5
or
\num{3,5} or \num{3.5} with siunitx configured correctly
or with the package icomma.

(Also, when already using the locale set to german, one could be expecting \cdot rather than \times. There should be an option to choose between these)

Operating system

No response

Matplotlib Version

3.5.3

Matplotlib Backend

module://matplotlib_inline.backend_inline

Python version

3.9.7

Jupyter version

6.4.10

Installation

pip