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https://github.com/asottile/pyupgrade

A tool (and pre-commit hook) to automatically upgrade syntax for newer versions of the language.
https://github.com/asottile/pyupgrade

linter pre-commit python

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

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pyupgrade

=========



A tool (and pre-commit hook) to automatically upgrade syntax for newer

versions of the language.



## Installation



```bash

pip install pyupgrade

```



## As a pre-commit hook



See [pre-commit](https://github.com/pre-commit/pre-commit) for instructions



Sample `.pre-commit-config.yaml`:



```yaml

-   repo: https://github.com/asottile/pyupgrade

    rev: v3.19.0

    hooks:

    -   id: pyupgrade

```



## Implemented features



### Set literals



```diff

-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



```diff

-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}

```



### Replace unnecessary lambdas in `collections.defaultdict` calls



```diff

-defaultdict(lambda: [])

+defaultdict(list)

-defaultdict(lambda: list())

+defaultdict(list)

-defaultdict(lambda: {})

+defaultdict(dict)

-defaultdict(lambda: dict())

+defaultdict(dict)

-defaultdict(lambda: ())

+defaultdict(tuple)

-defaultdict(lambda: tuple())

+defaultdict(tuple)

-defaultdict(lambda: set())

+defaultdict(set)

-defaultdict(lambda: 0)

+defaultdict(int)

-defaultdict(lambda: 0.0)

+defaultdict(float)

-defaultdict(lambda: 0j)

+defaultdict(complex)

-defaultdict(lambda: '')

+defaultdict(str)

```



### Format Specifiers



```diff

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

+'{} {}'.format(1, 2)

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

+'{}' '{}'.format(1, 2)

```



### printf-style string formatting



Availability:

- Unless `--keep-percent-format` is passed.



```diff

-'%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)

```



### Unicode literals



```diff

-u'foo'

+'foo'

-u"foo"

+'foo'

-u'''foo'''

+'''foo'''

```



### Invalid escape sequences



```diff

 # strings with only invalid sequences become raw strings

-'\d'

+r'\d'

 # strings with mixed valid / invalid sequences get escaped

-'\n\d'

+'\n\\d'

-u'\d'

+r'\d'

 # this fixes a syntax error in python3.3+

-'\N'

+r'\N'

```



### `is` / `is not` comparison to constant literals



In python3.8+, comparison to literals becomes a `SyntaxWarning` as the success

of those comparisons is implementation specific (due to common object caching).



```diff

-x is 5

+x == 5

-x is not 5

+x != 5

-x is 'foo'

+x == 'foo'

```



### `.encode()` to bytes literals



```diff

-'foo'.encode()

+b'foo'

-'foo'.encode('ascii')

+b'foo'

-'foo'.encode('utf-8')

+b'foo'

-u'foo'.encode()

+b'foo'

-'\xa0'.encode('latin1')

+b'\xa0'

```



### extraneous parens in `print(...)`



A fix for [python-modernize/python-modernize#178]



```diff

 # ok: printing an empty tuple

 print(())

 # ok: printing a tuple

 print((1,))

 # ok: parenthesized generator argument

 sum((i for i in range(3)), [])

 # fixed:

-print(("foo"))

+print("foo")

```



[python-modernize/python-modernize#178]: https://github.com/python-modernize/python-modernize/issues/178



### constant fold `isinstance` / `issubclass` / `except`



```diff

-isinstance(x, (int, int))

+isinstance(x, int)



-issubclass(y, (str, str))

+issubclass(y, str)



 try:

     raises()

-except (Error1, Error1, Error2):

+except (Error1, Error2):

     pass

```



### unittest deprecated aliases



Rewrites [deprecated unittest method aliases](https://docs.python.org/3/library/unittest.html#deprecated-aliases) to their non-deprecated forms.



```diff

 from unittest import TestCase



 class MyTests(TestCase):

     def test_something(self):

-        self.failUnlessEqual(1, 1)

+        self.assertEqual(1, 1)

-        self.assertEquals(1, 1)

+        self.assertEqual(1, 1)

```



### `super()` calls



```diff

 class C(Base):

     def f(self):

-        super(C, self).f()

+        super().f()

```



### "new style" classes



#### rewrites class declaration



```diff

-class C(object): pass

+class C: pass

-class C(B, object): pass

+class C(B): pass

```



#### removes `__metaclass__ = type` declaration



```diff

 class C:

-    __metaclass__ = type

```



### forced `str("native")` literals



```diff

-str()

+''

-str("foo")

+"foo"

```



### `.encode("utf-8")`



```diff

-"foo".encode("utf-8")

+"foo".encode()

```



### `# coding: ...` comment



as of [PEP 3120], the default encoding for python source is UTF-8



```diff

-# coding: utf-8

 x = 1

```



[PEP 3120]: https://www.python.org/dev/peps/pep-3120/



### `__future__` import removal



Availability:

- by default removes `nested_scopes`, `generators`, `with_statement`,

  `absolute_import`, `division`, `print_function`, `unicode_literals`

- `--py37-plus` will also remove `generator_stop`



```diff

-from __future__ import with_statement

```



### Remove unnecessary py3-compat imports



```diff

-from io import open

-from six.moves import map

-from builtins import object  # python-future

```



### import replacements



Availability:

- `--py36-plus` (and others) will replace imports



see also [reorder-python-imports](https://github.com/asottile/reorder_python_imports#removing--rewriting-obsolete-six-imports)



some examples:



```diff

-from collections import deque, Mapping

+from collections import deque

+from collections.abc import Mapping

```



```diff

-from typing import Sequence

+from collections.abc import Sequence

```



```diff

-from typing_extensions import Concatenate

+from typing import Concatenate

```



### rewrite `mock` imports



Availability:

- [Unless `--keep-mock` is passed on the commandline](https://github.com/asottile/pyupgrade/issues/314).



```diff

-from mock import patch

+from unittest.mock import patch

```



### `yield` => `yield from`



```diff

 def f():

-    for x in y:

-        yield x

+    yield from y

-    for a, b in c:

-        yield (a, b)

+    yield from c

```



### Python2 and old Python3.x blocks



```diff

 import sys

-if sys.version_info < (3,):  # also understands `six.PY2` (and `not`), `six.PY3` (and `not`)

-    print('py2')

-else:

-    print('py3')

+print('py3')

```



Availability:

- `--py36-plus` will remove Python <= 3.5 only blocks

- `--py37-plus` will remove Python <= 3.6 only blocks

- so on and so forth



```diff

 # using --py36-plus for this example



 import sys

-if sys.version_info < (3, 6):

-    print('py3.5')

-else:

-    print('py3.6+')

+print('py3.6+')



-if sys.version_info <= (3, 5):

-    print('py3.5')

-else:

-    print('py3.6+')

+print('py3.6+')



-if sys.version_info >= (3, 6):

-    print('py3.6+')

-else:

-    print('py3.5')

+print('py3.6+')

```



Note that `if` blocks without an `else` will not be rewritten as it could introduce a syntax error.



### remove `six` compatibility code



```diff

-six.text_type

+str

-six.binary_type

+bytes

-six.class_types

+(type,)

-six.string_types

+(str,)

-six.integer_types

+(int,)

-six.unichr

+chr

-six.iterbytes

+iter

-six.print_(...)

+print(...)

-six.exec_(c, g, l)

+exec(c, g, l)

-six.advance_iterator(it)

+next(it)

-six.next(it)

+next(it)

-six.callable(x)

+callable(x)

-six.moves.range(x)

+range(x)

-six.moves.xrange(x)

+range(x)



-from six import text_type

-text_type

+str



[email protected]_2_unicode_compatible

 class C:

     def __str__(self):

         return u'C()'



-class C(six.Iterator): pass

+class C: pass



-class C(six.with_metaclass(M, B)): pass

+class C(B, metaclass=M): pass



[email protected]_metaclass(M)

-class C(B): pass

+class C(B, metaclass=M): pass



-isinstance(..., six.class_types)

+isinstance(..., type)

-issubclass(..., six.integer_types)

+issubclass(..., int)

-isinstance(..., six.string_types)

+isinstance(..., str)



-six.b('...')

+b'...'

-six.u('...')

+'...'

-six.byte2int(bs)

+bs[0]

-six.indexbytes(bs, i)

+bs[i]

-six.int2byte(i)

+bytes((i,))

-six.iteritems(dct)

+dct.items()

-six.iterkeys(dct)

+dct.keys()

-six.itervalues(dct)

+dct.values()

-next(six.iteritems(dct))

+next(iter(dct.items()))

-next(six.iterkeys(dct))

+next(iter(dct.keys()))

-next(six.itervalues(dct))

+next(iter(dct.values()))

-six.viewitems(dct)

+dct.items()

-six.viewkeys(dct)

+dct.keys()

-six.viewvalues(dct)

+dct.values()

-six.create_unbound_method(fn, cls)

+fn

-six.get_unbound_function(meth)

+meth

-six.get_method_function(meth)

+meth.__func__

-six.get_method_self(meth)

+meth.__self__

-six.get_function_closure(fn)

+fn.__closure__

-six.get_function_code(fn)

+fn.__code__

-six.get_function_defaults(fn)

+fn.__defaults__

-six.get_function_globals(fn)

+fn.__globals__

-six.raise_from(exc, exc_from)

+raise exc from exc_from

-six.reraise(tp, exc, tb)

+raise exc.with_traceback(tb)

-six.reraise(*sys.exc_info())

+raise

-six.assertCountEqual(self, a1, a2)

+self.assertCountEqual(a1, a2)

-six.assertRaisesRegex(self, e, r, fn)

+self.assertRaisesRegex(e, r, fn)

-six.assertRegex(self, s, r)

+self.assertRegex(s, r)



 # note: only for *literals*

-six.ensure_binary('...')

+b'...'

-six.ensure_str('...')

+'...'

-six.ensure_text('...')

+'...'

```



### `open` alias



```diff

-with io.open('f.txt') as f:

+with open('f.txt') as f:

     ...

```



### redundant `open` modes



```diff

-open("foo", "U")

+open("foo")

-open("foo", "Ur")

+open("foo")

-open("foo", "Ub")

+open("foo", "rb")

-open("foo", "rUb")

+open("foo", "rb")

-open("foo", "r")

+open("foo")

-open("foo", "rt")

+open("foo")

-open("f", "r", encoding="UTF-8")

+open("f", encoding="UTF-8")

-open("f", "wt")

+open("f", "w")

```



### `OSError` aliases



```diff

 # also understands:

 # - IOError

 # - WindowsError

 # - mmap.error and uses of `from mmap import error`

 # - select.error and uses of `from select import error`

 # - socket.error and uses of `from socket import error`



 def throw():

-    raise EnvironmentError('boom')

+    raise OSError('boom')



 def catch():

     try:

         throw()

-    except EnvironmentError:

+    except OSError:

         handle_error()

```



### `TimeoutError` aliases



Availability:

- `--py310-plus` for `socket.timeout`

- `--py311-plus` for `asyncio.TimeoutError`



```diff



 def throw(a):

     if a:

-        raise asyncio.TimeoutError('boom')

+        raise TimeoutError('boom')

     else:

-        raise socket.timeout('boom')

+        raise TimeoutError('boom')



 def catch(a):

     try:

         throw(a)

-    except (asyncio.TimeoutError, socket.timeout):

+    except TimeoutError:

         handle_error()

```



### `typing.Text` str alias



```diff

-def f(x: Text) -> None:

+def f(x: str) -> None:

     ...

```



### Unpacking list comprehensions



```diff

-foo, bar, baz = [fn(x) for x in items]

+foo, bar, baz = (fn(x) for x in items)

```



### Rewrite `xml.etree.cElementTree` to `xml.etree.ElementTree`



```diff

-import xml.etree.cElementTree as ET

+import xml.etree.ElementTree as ET

-from xml.etree.cElementTree import XML

+from xml.etree.ElementTree import XML

```



### Rewrite `type` of primitive



```diff

-type('')

+str

-type(b'')

+bytes

-type(0)

+int

-type(0.)

+float

```



### `typing.NamedTuple` / `typing.TypedDict` py36+ syntax



Availability:

- `--py36-plus` is passed on the commandline.



```diff

-NT = typing.NamedTuple('NT', [('a', int), ('b', Tuple[str, ...])])

+class NT(typing.NamedTuple):

+    a: int

+    b: Tuple[str, ...]



-D1 = typing.TypedDict('D1', a=int, b=str)

+class D1(typing.TypedDict):

+    a: int

+    b: str



-D2 = typing.TypedDict('D2', {'a': int, 'b': str})

+class D2(typing.TypedDict):

+    a: int

+    b: str

```



### f-strings



Availability:

- `--py36-plus` is passed on the commandline.



```diff

-'{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}'

-'{} {}'.format(f(), g())

+f'{f()} {g()}'

-'{x}'.format(**locals())

+f'{x}'

```



_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

sufficiently complicated (as this can decrease readability).



### `subprocess.run`: replace `universal_newlines` with `text`



Availability:

- `--py37-plus` is passed on the commandline.



```diff

-output = subprocess.run(['foo'], universal_newlines=True)

+output = subprocess.run(['foo'], text=True)

```



### `subprocess.run`: replace `stdout=subprocess.PIPE, stderr=subprocess.PIPE` with `capture_output=True`



Availability:

- `--py37-plus` is passed on the commandline.



```diff

-output = subprocess.run(['foo'], stdout=subprocess.PIPE, stderr=subprocess.PIPE)

+output = subprocess.run(['foo'], capture_output=True)

```



### remove parentheses from `@functools.lru_cache()`



Availability:

- `--py38-plus` is passed on the commandline.



```diff

 import functools



[email protected]_cache()

[email protected]_cache

 def expensive():

     ...

```



### shlex.join



Availability:

- `--py38-plus` is passed on the commandline.



```diff

-' '.join(shlex.quote(arg) for arg in cmd)

+shlex.join(cmd)

```



### replace `@functools.lru_cache(maxsize=None)` with shorthand



Availability:

- `--py39-plus` is passed on the commandline.



```diff

 import functools



[email protected]_cache(maxsize=None)

[email protected]

 def expensive():

     ...

```



### pep 585 typing rewrites



Availability:

- File imports `from __future__ import annotations`

    - Unless `--keep-runtime-typing` is passed on the commandline.

- `--py39-plus` is passed on the commandline.



```diff

-def f(x: List[str]) -> None:

+def f(x: list[str]) -> None:

     ...

```



### pep 604 typing rewrites



Availability:

- File imports `from __future__ import annotations`

    - Unless `--keep-runtime-typing` is passed on the commandline.

- `--py310-plus` is passed on the commandline.



```diff

-def f() -> Optional[str]:

+def f() -> str | None:

     ...

```



```diff

-def f() -> Union[int, str]:

+def f() -> int | str:

     ...

```



### pep 696 TypeVar defaults



Availability:

- File imports `from __future__ import annotations`

    - Unless `--keep-runtime-typing` is passed on the commandline.

- `--py313-plus` is passed on the commandline.



```diff

-def f() -> Generator[int, None, None]:

+def f() -> Generator[int]:

     yield 1

```



```diff

-async def f() -> AsyncGenerator[int, None]:

+async def f() -> AsyncGenerator[int]:

     yield 1

```



### remove quoted annotations



Availability:

- File imports `from __future__ import annotations`



```diff

-def f(x: 'queue.Queue[int]') -> C:

+def f(x: queue.Queue[int]) -> C:

```



### use `datetime.UTC` alias



Availability:

- `--py311-plus` is passed on the commandline.



```diff

 import datetime



-datetime.timezone.utc

+datetime.UTC

```