Sounds awfully premature. Style guides are typically updated in response to the occurrence of bad practice in the wild, not in anticipation of such bad practice. I would give the users of Python 3.6 some more credit.
On Tue, Sep 8, 2015 at 12:17 AM, Mike Miller <python-...@mgmiller.net> wrote: > Hi, > > I'd like to collect thinking on best practices that we can use as a style > guide for string interpolation. Now that arbitrary expressions are very > likely to be included, it is more important to set guidelines than it would > otherwise be. > > Below is a recent post with some good ideas (though it hopes to restrict > expressions, which is not what we're discussing here, but rather creation > of a style-guide for code-review a la PEP8). > > Would anyone else like to contribute? > > -Mike > > Recent posts: > > - On PEPs to augment PEP8: > > > https://mail.python.org/pipermail/python-dev/2015-September/141473.html > > - On things to avoid in f-strings: > > > https://mail.python.org/pipermail/python-dev/2015-September/141451.html > (part included below) > > > On 09/05/2015 02:10 AM, haypo s (Victor Stinner) wrote: > > Would it be possible to specify a subset of the Python language > > allowed in f-string? For example, __import__ or lambda should not be > > used in a f-string. I'm not convinced that a loop or > > list/dict/set-comprehension is a good idea neither. > > > > I would prefer to keep as much code as possible *outside* f-string > because: > > - text editor knows well how to color it > > - static analyzers know how to analyze it > > - it encourage developers to indent and comment their code correctly, > > whereas f-string has more restrictons on indentation (is it possible > > to indent and comment code inside a f-string?) > > > > For example, for me it's a common practice to write a complex > > list-comprehension on two lines for readability: > > > > newlist = [very_complex_expression(item) > > for item in oldlist] > > # sorry, it's hard to indent correctly in a mail client, especially Gmail > > > > Well, I'm not convinced that we need a larger subset than what is > > allowed currently in str.format(), simple expressions like: obj.attr, > > obj[index], etc. > > > > I recall horrible examples in the previous mail threads showing how > > much complex code you can put inside f-string. > > > > Even the following example from the PEP seems too complex to me: > > print(f"Usage: {sys.argv[0]} [{'|'.join('--'+opt for opt in > > valid_opts)}]", file=sys.stderr) > > > > Oh, first I read [...] as a list-comprehension :-p But it's part of > > the output string, not of the Python code... > > > > I prefer to build the second parameter outside the f-string: > > opts = '|'.join('--'+opt for opt in valid_opts) > > print(f"Usage: {sys.argv[0]} [{opts}]", file=sys.stderr) > > > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > https://mail.python.org/mailman/options/python-dev/guido%40python.org > -- --Guido van Rossum (python.org/~guido)
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