Author serhiy.storchaka
Recipients eric.smith, serhiy.storchaka
Date 2016-09-29.08:50:04
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Message-id <1475139004.07.0.645331102167.issue28308@psf.upfronthosting.co.za>
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For now using formatted string literals (PEP498) is the fastest way of formatting strings.

$ ./python -m perf timeit -s 'k = "foo"; v = "bar"' -- '"{!s} = {!r}".format(k, v)'
Median +- std dev: 3.96 us +- 0.17 us

$ ./python -m perf timeit -s 'k = "foo"; v = "bar"' -- 'f"{k!s} = {v!r}"'
Median +- std dev: 1.09 us +- 0.08 us

The compiler could translate new-style formatting with literal format string to the equivalent formatted string literal. The code '{!s} = {!r}'.format(k, v) could be translated to

    t1 = k; t2 = v; f'{t1!r} = {t2!s}'; del t1, t2

or even simpler if k and v are initialized local variables.

$ ./python -m perf timeit -s 'k = "foo"; v = "bar"' -- 't1 = k; t2 = v; f"{t1!s} = {t2!r}"; del t1, t2'
Median +- std dev: 1.22 us +- 0.05 us

This is not easy issue and needs first implementing the AST optimizer.
History
Date User Action Args
2016-09-29 08:50:04serhiy.storchakasetrecipients: + serhiy.storchaka, eric.smith
2016-09-29 08:50:04serhiy.storchakasetmessageid: <1475139004.07.0.645331102167.issue28308@psf.upfronthosting.co.za>
2016-09-29 08:50:04serhiy.storchakalinkissue28308 messages
2016-09-29 08:50:04serhiy.storchakacreate