[python] added f-strings to helpers/parameter_generator.py

[NovusEdge]

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[NovusEdge]

#4136

[jameslamb]

I merged in the latest changes from the master branch to this PR tonight, following the steps described in #4144 (review).

I also patched a few small mistakes in 63ebdaf.

Importantly, the linting errors observed in #4146 (comment) were a result of incorrect escaping of literal curly braces. I learned tonight, from https://docs.python.org/3/library/string.html#format-string-syntax, that you should use a {{ to indicate a literal { (and }} for a literal }) in an f-string.

x = "hello"
f"{x}, {{curly braces}}"

# 'hello, {curly braces}'

I also ran python helpers/parameter_generator.py to be sure that the changes don't change the output produced by that script.

@StrikerRUS I think this is now ready for review.

[jameslamb]

These changes look good to me, but since I added a few changes I don't think my approval should count towards a merge.

[StrikerRUS]

Ah, missed one suggestion:

LightGBM/helpers/parameter_generator.py

Line 300 in 08d1ce4

str_to_write += " std::string tmp_str = \"\";\n"

This string is not needed to be converted into f-string. But I think we can change outer " quotes to ' ones to remove escaping in this PR.

[jameslamb]

Ah, missed one suggestion:

LightGBM/helpers/parameter_generator.py

Line 300 in 08d1ce4

str_to_write += " std::string tmp_str = \"\";\n"

This string is not needed to be converted into f-string. But I think we can change outer " quotes to ' ones to remove escaping in this PR.

ok. Updated in 62f3380

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