[python-package] f-string format updated in plot_example.py

[amanjha8100]

Contributes to #4136.

[amanjha8100]

Hello, @jameslamb sir, I am not able to understand why the continous-integration/appveyor/pr check failed. Can you give me some insight?

[jameslamb]

Since this is your first contribution to LightGBM, maintainers have to manually approve each CI run for GitHub Actions. That is a mechanism GitHub put in place a few months ago to prevent abuse.

You can click "details" next to the job continuous-integration/appveyor/pr to see what went wrong. I can see in the logs the following error from running the example you've changed in this pull request.

C:\projects\lightgbm\examples\python-guide\plot_example.py:51: UserWarning: Matplotlib is currently using agg, which is a non-GUI backend, so cannot show the figure.
  plt.show()
Plotting feature importances...
C:\projects\lightgbm\examples\python-guide\plot_example.py:55: UserWarning: Matplotlib is currently using agg, which is a non-GUI backend, so cannot show the figure.
  plt.show()
Plotting split value histogram...
Traceback (most recent call last):
  File "C:\projects\lightgbm\examples\python-guide\plot_example.py", line 58, in <module>
    ax = lgb.plot_split_value_histogram(gbm, feature='f26', bins='auto')
  File "C:\Miniconda37-x64\envs\test-env\lib\site-packages\lightgbm\plotting.py", line 233, in plot_split_value_histogram
    raise ValueError('Cannot plot split value histogram, '
ValueError: Cannot plot split value histogram, because feature f26 was not used in splitting

This probably means you've made a mistake in your changes. I will be able to look more closely and help later, but you might find it's faster to test your changes by running that single example locally before pushing another commit.

cd python-package
python setup.py install
cd ../examples/python-guide
python plot_example.py

[amanjha8100]

Well, I have committed the change. I am a little newbie to open-source, thanks for your help @jameslamb.

[amanjha8100]

Well, sir because of that, will the PR not get merged?

[amanjha8100]

Hey, @StrikerRUS is it okay now?

[jameslamb]

changes look good to me, thanks

[amanjha8100]

Hey, @StrikerRUS and @guolinke could you please review the changes.😊

[StrikerRUS]

LGTM, thanks!

[github-actions]

This pull request has been automatically locked since there has not been any recent activity since it was closed. To start a new related discussion, open a new issue at https://github.com/microsoft/LightGBM/issues including a reference to this.