A tool (and pre-commit hook) to automatically upgrade syntax for newer versions of the language.
Python
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README.md

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pyupgrade

A tool (and pre-commit hook) to automatically upgrade syntax for newer versions of the language.

Installation

pip install pyupgrade

As a pre-commit hook

See pre-commit for instructions

Sample .pre-commit-config.yaml:

-   repo: https://github.com/asottile/pyupgrade
    rev: v1.4.0
    hooks:
    -   id: pyupgrade

Implemented features

Set literals

set(())              # set()
set([])              # set()
set((1,))            # {1}
set((1, 2))          # {1, 2}
set([1, 2])          # {1, 2}
set(x for x in y)    # {x for x in y}
set([x for x in y])  # {x for x in y}

Dictionary comprehensions

dict((a, b) for a, b in y)   # {a: b for a, b in y}
dict([(a, b) for a, b in y)  # {a: b for a, b in y}

Python2.7+ Format Specifiers

'{0} {1}'.format(1, 2)    # '{} {}'.format(1, 2)
'{0}' '{1}'.format(1, 2)  # '{}' '{}'.format(1, 2)

printf-style string formatting

'%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)

Key format (%(key)s) rewriting is planned but not yet implemented.

Unicode literals

Availability:

  • File imports from __future__ import unicode_literals
  • --py3-plus is passed on the commandline.
u'foo'      # 'foo'
u"foo"      # 'foo'
u'''foo'''  # '''foo'''

Long literals

Availability:

  • If pyupgrade is running in python 2.
5L                            # 5
5l                            # 5
123456789123456789123456789L  # 123456789123456789123456789

Octal literals

Availability:

  • If pyupgrade is running in python 2.
0755  # 0o755

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).