Fix #2681

[jeskowagner]

Checks if current axis is colorbar before trying to set the name, see #2681.
This might not be the best solution and does not yet integrate a unit test.

[codecov]

Codecov Report

Merging #2682 (e762eac) into master (616d580) will decrease coverage by 0.02%.
The diff coverage is 0.00%.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2682      +/-   ##
==========================================
- Coverage   71.98%   71.97%   -0.02%     
==========================================
  Files         108      108              
  Lines       11905    11907       +2     
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  Hits         8570     8570              
- Misses       3335     3337       +2     

Files	Coverage Δ
scanpy/plotting/_tools/scatterplots.py	86.82% <0.00%> (-0.42%)	⬇️

[flying-sheep]

Where does the string '<colorbar>' come from?

[jeskowagner]

Continuing from the reproducible example in #2681, I debugged from this line onwards. I.e. we can do

from scanpy.plotting import embedding

label_dict = {
    'PC{}'.format(i + 1): 'PC{} ({}%)'.format(i + 1, round(v * 100, 2))
    for i, v in enumerate(adata.uns['pca']['variance_ratio'])
}
# {'PC1': 'PC1 (27.22%)', 'PC2': 'PC2 (23.11%)', 'PC3': 'PC3 (18.64%)', 'PC4': 'PC4 (15.85%)'}

fig = embedding(adata, 'pca', return_fig=True, color="a")

To then get the label:

for i, ax in enumerate(fig.axes):
    print(f"Axis {i}")
    print(f"Label: {ax.get_label()}")
    print(f"x: {ax.xaxis.get_label().get_text()}")
    print(f"y: {ax.yaxis.get_label().get_text()}")
    print("")

Which prints:

Axis 0
Label: 
x: PC1
y: PC2

Axis 1
Label: <colorbar>
x: 
y: 

An alternative fix could also check for key presence in the label_dict:

for ax in fig.axes:
    xlab = ax.xaxis.get_label().get_text()
    if xlab in label_dict:
        ax.set_xlabel(xlab)
    ylab = ax.yaxis.get_label().get_text()
    if ylab in label_dict:
        ax.set_ylabel(ylab)

[flying-sheep]

I think the alternative version is safer, as it’ll work even if they change the format of that autogenerated label.

Unless they document it somewhere that it’s that, I assume it’s an implementation detauil.

[jeskowagner]

Great, thank you!