Remove Python 2 support.

Closes #97.

.appveyor.yml

@@ -4,8 +4,9 @@ os: "Visual Studio 2019"
 
 environment:
   matrix:
-    - PYTHON: "C:\\Python27"
-    - PYTHON: "C:\\Python37"
+    # https://www.appveyor.com/docs/windows-images-software/#python
+    # TODO: Update to Python 3.8 once AppVeyor makes it available.
+    - PYTHON: "C:\\Python37-x64"
 
 build_script:
   - "git --no-pager log -n2"

.travis.yml

@@ -109,21 +109,11 @@ matrix:
     - python: '3.8'
       env: 'TASK=test-linux-cpython-3.8 COVERAGE=1'
 
-    - python: '2.7'
-      env: 'TASK=test-linux-cpython-2.7 COVERAGE=1'
-
     - python: 'pypy3'
       env: 'TASK=test-linux-pypy3 COVERAGE=1'
 
-    - python: 'pypy'
-      env: 'TASK=test-linux-pypy COVERAGE=1'
-
-    ## Test suite on Mac with latest CPython 2 and 3.
-    - python: '2.7'
-      env: 'TASK=test-mac-cpython-2.7'
-      os: 'osx'
-      language: 'generic'
-
+    ## Test suite on Mac with latest CPython 3.
+    ## TODO: Update to 3.8 once 'python-framework-38' cask is available.
     - python: '3.7'
       env: 'TASK=test-mac-cpython-3.7'
       os: 'osx'

CHANGELOG.rst

@@ -26,6 +26,18 @@ click "`Watch <https://help.github.com/en/articles/watching-and-unwatching-relea
 and choose "Releases".
 
 
+0.19.0 (not yet released)
+-------------------------
+
+Drop support for Python 2
+:ref:`as promised in v0.18.2 <changelog:0.18.2 (2019-09-08)>`.
+
+The :mod:`bidict.compat` module has been pruned accordingly.
+
+This makes bidict more efficient on Python 3
+and enables further improvement to bidict in the future.
+
+
 0.18.3 (2019-09-22)
 -------------------
 

README.rst

@@ -76,7 +76,7 @@ Bidict:
   Bloomberg, Two Sigma, and others
 - has carefully designed APIs for
   safety, simplicity, flexibility, and ergonomics
-- is CPython-, PyPy-, Python 2-, and Python 3-compatible
+- is CPython- and PyPy3-compatible [#fn-py2]_
 - has extensive test coverage
   (including property-based tests and benchmarks)
   run continuously on all supported Python versions and OSes
@@ -85,13 +85,15 @@ Bidict:
   that leverages a number of advanced language features [#fn-learning]_
 
 
-⚠️ Python 2 EOL ⚠️
-++++++++++++++++++
-
-Python 2 support will be dropped in a future release.
-
-See `python3statement.org <https://python3statement.org>`__
-for more info.
+.. [#fn-py2] As promised in the
+   :ref:`0.18.2 release <changelog:0.18.2 (2019-09-08)>`,
+   **Python 2 is no longer supported**.
+   :ref:`Version 0.18.3 <changelog:0.18.3 (2019-09-22)>`
+   is the last release of bidict that supports Python 2.
+   This makes bidict more efficient on Python 3
+   and enables further improvement to bidict in the future.
+   See `python3statement.org <https://python3statement.org>`__
+   for more info.
 
 
 Installation

bidict/__init__.py

@@ -48,9 +48,20 @@
 .. :license: MPLv2. See LICENSE for details.
 """
 
-# This __init__.py only collects functionality implemented in the rest of the
-# source and exports it under the `bidict` module namespace (via `__all__`).
+from warnings import warn
+from .compat import PY2, PYMAJOR, PYMINOR
+
+if PY2:
+    raise ImportError('Python 3.5+ is required.')
+
+# Assume Python 3 when not PY2, but explicitly check before showing this warning.
+if PYMAJOR == 3 and PYMINOR < 5:  # pragma: no cover
+    warn('Python 3.4 and below are not supported.')
 
+
+# The rest of this file only collects functionality implemented in the rest of the
+# source and exports it under the `bidict` module namespace (via `__all__`).
+# pylint: disable=wrong-import-position
 from ._abc import BidirectionalMapping
 from ._base import BidictBase
 from ._mut import MutableBidict

bidict/_abc.py

@@ -28,7 +28,8 @@
 
 """Provides the :class:`BidirectionalMapping` abstract base class."""
 
-from .compat import Mapping, abstractproperty, iteritems
+from abc import abstractmethod
+from collections.abc import Mapping
 
 
 class BidirectionalMapping(Mapping):  # pylint: disable=abstract-method,no-init
@@ -48,7 +49,8 @@ class BidirectionalMapping(Mapping):  # pylint: disable=abstract-method,no-init
 
     __slots__ = ()
 
-    @abstractproperty
+    @property
+    @abstractmethod
     def inverse(self):
         """The inverse of this bidirectional mapping instance.
 
@@ -77,7 +79,7 @@ def __inverted__(self):
 
         *See also* :func:`bidict.inverted`
         """
-        return iteritems(self.inverse)
+        return iter(self.inverse.items())
 
     @classmethod
     def __subclasshook__(cls, C):  # noqa: N803 (argument name should be lowercase)

bidict/_base.py

@@ -29,6 +29,7 @@
 """Provides :class:`BidictBase`."""
 
 from collections import namedtuple
+from collections.abc import Mapping
 from weakref import ref
 
 from ._abc import BidirectionalMapping
@@ -38,7 +39,6 @@
 from ._miss import _MISS
 from ._noop import _NOOP
 from ._util import _iteritems_args_kw
-from .compat import PY2, KeysView, ItemsView, Mapping, iteritems
 
 
 _DedupResult = namedtuple('_DedupResult', 'isdupkey isdupval invbyval fwdbykey')
@@ -57,7 +57,7 @@
 class BidictBase(BidirectionalMapping):
     """Base class implementing :class:`BidirectionalMapping`."""
 
-    __slots__ = ('_fwdm', '_invm', '_inv', '_invweak', '_hash') + (() if PY2 else ('__weakref__',))
+    __slots__ = ('_fwdm', '_invm', '_inv', '_invweak', '_hash', '__weakref__')
 
     #: The default :class:`DuplicationPolicy`
     #: (in effect during e.g. :meth:`~bidict.bidict.__init__` calls)
@@ -196,7 +196,7 @@ def __setstate__(self, state):
 
         *See also* :meth:`object.__setstate__`
         """
-        for slot, value in iteritems(state):
+        for slot, value in state.items():
             setattr(self, slot, value)
         self._init_inv()
 
@@ -205,7 +205,7 @@ def __repr__(self):
         clsname = self.__class__.__name__
         if not self:
             return '%s()' % clsname
-        return '%s(%r)' % (clsname, self._repr_delegate(iteritems(self)))
+        return '%s(%r)' % (clsname, self._repr_delegate(self.items()))
 
     # The inherited Mapping.__eq__ implementation would work, but it's implemented in terms of an
     # inefficient ``dict(self.items()) == dict(other.items())`` comparison, so override it with a
@@ -227,7 +227,7 @@ def __eq__(self, other):
         if not isinstance(other, Mapping) or len(self) != len(other):
             return False
         selfget = self.get
-        return all(selfget(k, _MISS) == v for (k, v) in iteritems(other))
+        return all(selfget(k, _MISS) == v for (k, v) in other.items())
 
     # The following methods are mutating and so are not public. But they are implemented in this
     # non-mutable base class (rather than the mutable `bidict` subclass) because they are used here
@@ -344,7 +344,7 @@ def _update(self, init, on_dup, *args, **kw):
 
     def _update_no_dup_check(self, other, _nodup=_NODUP):
         write_item = self._write_item
-        for (key, val) in iteritems(other):
+        for (key, val) in other.items():
             write_item(key, val, _nodup)
 
     def _update_no_rollback(self, on_dup, *args, **kw):
@@ -435,31 +435,6 @@ def values(self):
         """
         return self.inverse.keys()
 
-    if PY2:
-        # For iterkeys and iteritems, inheriting from Mapping already provides
-        # the best default implementations so no need to define here.
-
-        def itervalues(self):
-            """An iterator over the contained values."""
-            return self.inverse.iterkeys()
-
-        def viewkeys(self):  # noqa: D102; pylint: disable=missing-docstring
-            return KeysView(self)
-
-        def viewvalues(self):  # noqa: D102; pylint: disable=missing-docstring
-            return self.inverse.viewkeys()
-
-        viewvalues.__doc__ = values.__doc__
-        values.__doc__ = 'A list of the contained values.'
-
-        def viewitems(self):  # noqa: D102; pylint: disable=missing-docstring
-            return ItemsView(self)
-
-        # __ne__ added automatically in Python 3 when you implement __eq__, but not in Python 2.
-        def __ne__(self, other):  # noqa: N802
-            u"""*x.__ne__(other)　⟺　x != other*"""
-            return not self == other  # Implement __ne__ in terms of __eq__.
-
 
 #                             * Code review nav *
 #==============================================================================

bidict/_delegating_mixins.py

@@ -50,20 +50,11 @@
 :class:`sortedcontainers.SortedDict`s.
 """
 
-from .compat import PY2
 
-
-_KEYS_METHODS = ('keys',) + (('viewkeys', 'iterkeys') if PY2 else ())
-_ITEMS_METHODS = ('items',) + (('viewitems', 'iteritems') if PY2 else ())
 _DOCSTRING_BY_METHOD = {
     'keys': 'A set-like object providing a view on the contained keys.',
     'items': 'A set-like object providing a view on the contained items.',
 }
-if PY2:
-    _DOCSTRING_BY_METHOD['viewkeys'] = _DOCSTRING_BY_METHOD['keys']
-    _DOCSTRING_BY_METHOD['viewitems'] = _DOCSTRING_BY_METHOD['items']
-    _DOCSTRING_BY_METHOD['keys'] = 'A list of the contained keys.'
-    _DOCSTRING_BY_METHOD['items'] = 'A list of the contained items.'
 
 
 def _make_method(methodname):
@@ -79,13 +70,14 @@ def _make_fwdm_delegating_mixin(clsname, methodnames):
     return type(clsname, (object,), clsdict)
 
 
-_DelegateKeysToFwdm = _make_fwdm_delegating_mixin('_DelegateKeysToFwdm', _KEYS_METHODS)
-_DelegateItemsToFwdm = _make_fwdm_delegating_mixin('_DelegateItemsToFwdm', _ITEMS_METHODS)
+_DelegateKeysToFwdm = _make_fwdm_delegating_mixin('_DelegateKeysToFwdm', ('keys',))
+_DelegateItemsToFwdm = _make_fwdm_delegating_mixin('_DelegateItemsToFwdm', ('items',))
 _DelegateKeysAndItemsToFwdm = type(
     '_DelegateKeysAndItemsToFwdm',
     (_DelegateKeysToFwdm, _DelegateItemsToFwdm),
     {'__slots__': ()})
 
+
 #                             * Code review nav *
 #==============================================================================
 # ← Prev: _base.py    Current: _delegating_mixins.py   Next: _frozenbidict.py →

bidict/_frozenbidict.py

@@ -27,9 +27,10 @@
 
 """Provides :class:`frozenbidict`, an immutable, hashable bidirectional mapping type."""
 
+from collections.abc import ItemsView
+
 from ._base import BidictBase
 from ._delegating_mixins import _DelegateKeysAndItemsToFwdm
-from .compat import ItemsView
 
 
 class frozenbidict(_DelegateKeysAndItemsToFwdm, BidictBase):  # noqa: N801,E501; pylint: disable=invalid-name

bidict/_frozenordered.py

@@ -30,7 +30,7 @@
 from ._delegating_mixins import _DelegateKeysToFwdm
 from ._frozenbidict import frozenbidict
 from ._orderedbase import OrderedBidictBase
-from .compat import DICTS_ORDERED, PY2, izip
+from .compat import DICTS_ORDERED
 
 
 # If the Python implementation's dict type is ordered (e.g. PyPy or CPython >= 3.6), then
@@ -45,17 +45,11 @@
     # frozenbidict.__hash__ can be reused for FrozenOrderedBidict:
     # FrozenOrderedBidict inherits BidictBase.__eq__ which is order-insensitive,
     # and frozenbidict.__hash__ is consistent with BidictBase.__eq__.
-    __hash__=frozenbidict.__hash__.__func__ if PY2 else frozenbidict.__hash__,
+    __hash__=frozenbidict.__hash__,
     __doc__='Hashable, immutable, ordered bidict type.',
     __module__=__name__,  # Otherwise unpickling fails in Python 2.
 )
 
-# When PY2 (so we provide iteritems) and DICTS_ORDERED, e.g. on PyPy, the following implementation
-# of iteritems may be more efficient than that inherited from `Mapping`. This exploits the property
-# that the keys in `_fwdm` and `_invm` are already in the right order:
-if PY2 and DICTS_ORDERED:
-    _CLSDICT['iteritems'] = lambda self: izip(self._fwdm, self._invm)  # noqa: E501; pylint: disable=protected-access
-
 FrozenOrderedBidict = type('FrozenOrderedBidict', _BASES, _CLSDICT)  # pylint: disable=invalid-name
 
 

bidict/_mut.py

@@ -28,10 +28,11 @@
 
 """Provides :class:`bidict`."""
 
+from collections.abc import MutableMapping
+
 from ._base import BidictBase
 from ._dup import OVERWRITE, RAISE, _OnDup
 from ._miss import _MISS
-from .compat import MutableMapping
 
 
 # Extend MutableMapping explicitly because it doesn't implement __subclasshook__, as well as to
@@ -150,7 +151,7 @@ def popitem(self):
         del self._invm[val]
         return key, val
 
-    def update(self, *args, **kw):
+    def update(self, *args, **kw):  # pylint: disable=arguments-differ
         """Like :meth:`putall` with default duplication policies."""
         if args or kw:
             self._update(False, None, *args, **kw)

bidict/_named.py

@@ -7,16 +7,8 @@
 
 """Provides :func:`bidict.namedbidict`."""
 
-import re
-
 from ._abc import BidirectionalMapping
 from ._bidict import bidict
-from .compat import PY2
-
-
-_isidentifier = (  # pylint: disable=invalid-name
-    re.compile('[A-Za-z_][A-Za-z0-9_]*$').match if PY2 else str.isidentifier
-)
 
 
 def namedbidict(typename, keyname, valname, base_type=bidict):
@@ -56,7 +48,7 @@ def namedbidict(typename, keyname, valname, base_type=bidict):
     if not issubclass(base_type, BidirectionalMapping):
         raise TypeError(base_type)
     names = (typename, keyname, valname)
-    if not all(map(_isidentifier, names)) or keyname == valname:
+    if not all(map(str.isidentifier, names)) or keyname == valname:
         raise ValueError(names)
 
     class _Named(base_type):  # pylint: disable=too-many-ancestors
@@ -89,8 +81,7 @@ def __reduce__(self):
     setattr(_Named, fname, property(_Named._getfwd, doc=fdoc))  # pylint: disable=protected-access
     setattr(_Named, iname, property(_Named._getinv, doc=idoc))  # pylint: disable=protected-access
 
-    if not PY2:
-        _Named.__qualname__ = _Named.__qualname__[:-len(_Named.__name__)] + typename
+    _Named.__qualname__ = _Named.__qualname__[:-len(_Named.__name__)] + typename
     _Named.__name__ = typename
     return _Named