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: v3.21.2
    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}

Replace unnecessary lambdas in collections.defaultdict calls

-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

-'{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.

-'%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

-u'foo'
+'foo'
-u"foo"
+'foo'
-u'''foo'''
+'''foo'''

Invalid escape sequences

 # 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).

-x is 5
+x == 5
-x is not 5
+x != 5
-x is 'foo'
+x == 'foo'

.encode() to bytes literals

-'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

 # 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")

constant fold isinstance / issubclass / except

-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 to their non-deprecated forms.

 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

 class C(Base):
     def f(self):
-        super(C, self).f()
+        super().f()

"new style" classes

rewrites class declaration

-class C(object): pass
+class C: pass
-class C(B, object): pass
+class C(B): pass

removes __metaclass__ = type declaration

 class C:
-    __metaclass__ = type

forced str("native") literals

-str()
+''
-str("foo")
+"foo"

.encode("utf-8")

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

# coding: ... comment

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

-# coding: utf-8
 x = 1

__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

-from __future__ import with_statement

Remove unnecessary py3-compat imports

-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

some examples:

-from collections import deque, Mapping
+from collections import deque
+from collections.abc import Mapping

-from typing import Sequence
+from collections.abc import Sequence

-from typing_extensions import Concatenate
+from typing import Concatenate

rewrite mock imports

Availability:

• Unless --keep-mock is passed on the commandline.

-from mock import patch
+from unittest.mock import patch

yield => yield from

 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

 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

 # 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

-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

-@six.python_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

-@six.add_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

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

redundant open modes

-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

 # 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

Availabili