Is there a tool to automatically convert string formatting types to f-strings?
Question:
Since python 3.6, the shortest and most performant way to format values into a string are PEP 498 f-strings (e.g. f'Hello {name}').
Converting older formatting types ('Hello %s' % name, 'Hello {}'.format(name) ) to the new one in an existing code base appears to be a task that could be automated, however I could not find any tool doing this. Is there a tool to automatically convert literals using old string formatting to f-strings?
Answers:
You can use flynt to convert multiple python files to use f-strings.
To run it, you need a python 3.6+ interpreter. Then, its as simple as:
pip install flynt
flynt [relative or absolute path to the root of your project]
Keep in mind that it will change files in place, so it is advisable to commit those to git or SVC system of your preference.
Here is an article describing the pros and cons of f-strings:
Disclaimer: I am the author of flynt package.
It looks like pyupgrade is capable of both converting % formatting to format calls, and format calls to f-strings
printf-style string formatting
Availability:
Unless --keep-percent-format is passed.
'%s %s' % (a, b) # '{} {}'.format(a, b)
'%r %2f' % (a, b) # '{!r} {:2f}'.format(a, b)
'%(a)s %(b)s' % {'a': 1, 'b': 2} # '{a} {b}'.format(a=1, b=2)
f-strings
Availability:
--py36-plus is passed on the commandline.
'{foo} {bar}'.format(foo=foo, bar=bar) # f'{foo} {bar}'
'{} {}'.format(foo, bar) # f'{foo} {bar}'
'{} {}'.format(foo.bar, baz.womp} # f'{foo.bar} {baz.womp}'
note: pyupgrade is intentionally timid and will not create an f-string if it would make the expression longer or if the substitution parameters are anything but simple names or dotted names (as this can decrease readability).
Since python 3.6, the shortest and most performant way to format values into a string are PEP 498 f-strings (e.g. f'Hello {name}').
Converting older formatting types ('Hello %s' % name, 'Hello {}'.format(name) ) to the new one in an existing code base appears to be a task that could be automated, however I could not find any tool doing this. Is there a tool to automatically convert literals using old string formatting to f-strings?
You can use flynt to convert multiple python files to use f-strings.
To run it, you need a python 3.6+ interpreter. Then, its as simple as:
pip install flynt
flynt [relative or absolute path to the root of your project]
Keep in mind that it will change files in place, so it is advisable to commit those to git or SVC system of your preference.
Here is an article describing the pros and cons of f-strings:
Disclaimer: I am the author of flynt package.
It looks like pyupgrade is capable of both converting % formatting to format calls, and format calls to f-strings
printf-style string formatting
Availability:
Unless
--keep-percent-formatis passed.'%s %s' % (a, b) # '{} {}'.format(a, b) '%r %2f' % (a, b) # '{!r} {:2f}'.format(a, b) '%(a)s %(b)s' % {'a': 1, 'b': 2} # '{a} {b}'.format(a=1, b=2)
f-strings
Availability:
--py36-plusis passed on the commandline.'{foo} {bar}'.format(foo=foo, bar=bar) # f'{foo} {bar}' '{} {}'.format(foo, bar) # f'{foo} {bar}' '{} {}'.format(foo.bar, baz.womp} # f'{foo.bar} {baz.womp}'
note: pyupgrade is intentionally timid and will not create an f-string if it would make the expression longer or if the substitution parameters are anything but simple names or dotted names (as this can decrease readability).