[Bug]: cannot reset label of axis to center

[decacent]

Bug summary

When I do once of setting xlabel of ylabel to left of right, it cannot reset label of axis to center any way.

Code for reproduction

if I do once:
ax.set_xlabel("my label",loc="left ") 
or:
ax.set_xlabel("my label",loc="right")
the following will have no any effect:
ax.set_xlabel("my label",loc="center")

Actual outcome

No any output

Expected outcome

reset the label to center

Additional information

No response

Operating system

win 10 x64

Matplotlib Version

3.4.3 and 3.5

Matplotlib Backend

Qt5, Qt6,

Python version

3.9, 3,10

Jupyter version

No response

Installation

pip

[jklymak]

Confirmed. Note that if you do set_xlabel('label', loc='left'); set_xlabel('label', loc='right'); it works, so "center" is being ignored. This is an easy fix, so I'll mark as good first issue. It just needs a fix in set_xlabel and set_ylabel and it requires a test in test_axes.py.

@jklymak This seems to be just another elif clause in the function definition, right? Currently, the kwargs.update sets x=0 for left, x=1 for right. Should center then be x=2 or should this be renumbered? I'm not sure if I understand this correctly...

[hansinahuja]

@sveneschlbeck The position is scaled from [0, 1] so it should be 0.5. There was also another error in set_ylabel() where horizontalalignment was getting reset instead of verticalalignment
Making a PR, hope I didn't step on your toes there!