[python] Migrate to f-strings in python-package/lightgbm/sklearn.py

[akshitadixit]

Switches some string formatting in sklearn.py to use f-strings, as part of #4136.

[jameslamb]

Thanks for picking this up! Please see my comments below.

I also made one small change to the PR. I added a note to the description mentioning #4136, so that there is a link connecting this PR to a previous issue and vice versa. We use that linking feature heavily in this project, to keep track of the connections between different discussions.

[jameslamb]

looks good, thank you!

[StrikerRUS]

Please update the following lines within this PR as well

LightGBM/python-package/lightgbm/sklearn.py

Lines 535 to 536 in 211ef78

	if hasattr(self, '_' + key):
	setattr(self, '_' + key, value)

LightGBM/python-package/lightgbm/sklearn.py

Lines 997 to 998 in 211ef78

	+ ' ' * 12 + 'The evaluation positions of the specified metric.\n'
	+ ' ' * 8 + _early_stop + _after_early_stop)

(part about ' ' * x)

LightGBM/python-package/lightgbm/sklearn.py

Line 655 in 211ef78

raise TypeError('{} should be dict or list'.format(name))

[akshitadixit]

@StrikerRUS do I only change the ' '*x part or do I also modify the concatenation taking place there into an f-string as below?

space = " "
    fit.__doc__ = (f"{_before_early_stop}" \
                  f"eval_at : iterable of int, optional (default=(1, 2, 3, 4, 5))\n" \
                  f"{space*12} The evaluation positions of the specified metric.\n" \
                  f"{space*8} {_early_stop} {_after_early_stop}")

[StrikerRUS]

Originally I thought about only ' '*x part, but just saw that @jameslamb would prefer modifying concatenation as well: #4144 (comment). So, please modify it with concatenation.

BTW, there are some other places where concatenation can be eliminated with f-strings:

LightGBM/python-package/lightgbm/sklearn.py

Lines 705 to 711 in 211ef78

	fit.__doc__ = _lgbmmodel_doc_fit.format(
	X_shape="array-like or sparse matrix of shape = [n_samples, n_features]",
	y_shape="array-like of shape = [n_samples]",
	sample_weight_shape="array-like of shape = [n_samples] or None, optional (default=None)",
	init_score_shape="array-like of shape = [n_samples] or None, optional (default=None)",
	group_shape="array-like or None, optional (default=None)"
	) + "\n\n" + _lgbmmodel_doc_custom_eval_note

LightGBM/python-package/lightgbm/sklearn.py

Lines 825 to 831 in 211ef78

	_base_doc = LGBMModel.fit.__doc__
	_base_doc = (_base_doc[:_base_doc.find('group :')] # type: ignore
	+ _base_doc[_base_doc.find('eval_set :'):]) # type: ignore
	_base_doc = (_base_doc[:_base_doc.find('eval_class_weight :')]
	+ _base_doc[_base_doc.find('eval_init_score :'):])
	fit.__doc__ = (_base_doc[:_base_doc.find('eval_group :')]
	+ _base_doc[_base_doc.find('eval_metric :'):])

LightGBM/python-package/lightgbm/sklearn.py

Lines 898 to 902 in 211ef78

	_base_doc = LGBMModel.fit.__doc__
	_base_doc = (_base_doc[:_base_doc.find('group :')] # type: ignore
	+ _base_doc[_base_doc.find('eval_set :'):]) # type: ignore
	fit.__doc__ = (_base_doc[:_base_doc.find('eval_group :')]
	+ _base_doc[_base_doc.find('eval_metric :'):])

LightGBM/python-package/lightgbm/sklearn.py

Lines 990 to 992 in 211ef78

	_base_doc = LGBMModel.fit.__doc__
	fit.__doc__ = (_base_doc[:_base_doc.find('eval_class_weight :')] # type: ignore
	+ _base_doc[_base_doc.find('eval_init_score :'):]) # type: ignore

But I don't think we should replace concatenation with f-strings there because concatenation is more readable in those cases in my opinion. @jameslamb WDYT?

Also, please check the following comment about padding #4144 (comment).

[jameslamb]

But I don't think we should replace concatenation with f-strings there because concatenation is more readable in those cases in my opinion

Yes I agree with you.

[akshitadixit]

So I infer that no concatenations be migrated then.

[jameslamb]

yes, cases like the ones @StrikerRUS mentioned (where .format() was used to replace a shared template like _lgbmmodel_doc_fit or where there are just variables being added to each other but not string literals) do not need to be changed for this pull request

[jameslamb]

Please see my new round of comments, and let me know if you have any questions! If it seems like we're giving you confusing or contradictory suggestions I apologize.

[jameslamb]

looks great, thank you!

[StrikerRUS]

LGTM!

[github-actions]

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