mirror of
https://github.com/python/cpython.git
synced 2024-11-25 09:39:56 +01:00
482fe0477e
add private method to enum to support replacing global constants with Enum members: - search for candidate constants via supplied filter - create new enum class and members - insert enum class and replace constants with members via supplied module name - replace __reduce_ex__ with function that returns member name, so previous Python versions can unpickle modify IntEnum classes to use new method
565 lines
21 KiB
Python
565 lines
21 KiB
Python
import sys
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from collections import OrderedDict
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from types import MappingProxyType, DynamicClassAttribute
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__all__ = ['Enum', 'IntEnum', 'unique']
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def _is_descriptor(obj):
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"""Returns True if obj is a descriptor, False otherwise."""
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return (
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hasattr(obj, '__get__') or
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hasattr(obj, '__set__') or
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hasattr(obj, '__delete__'))
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def _is_dunder(name):
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"""Returns True if a __dunder__ name, False otherwise."""
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return (name[:2] == name[-2:] == '__' and
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name[2:3] != '_' and
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name[-3:-2] != '_' and
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len(name) > 4)
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def _is_sunder(name):
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"""Returns True if a _sunder_ name, False otherwise."""
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return (name[0] == name[-1] == '_' and
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name[1:2] != '_' and
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name[-2:-1] != '_' and
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len(name) > 2)
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def _make_class_unpicklable(cls):
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"""Make the given class un-picklable."""
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def _break_on_call_reduce(self, proto):
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raise TypeError('%r cannot be pickled' % self)
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cls.__reduce_ex__ = _break_on_call_reduce
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cls.__module__ = '<unknown>'
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class _EnumDict(dict):
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"""Track enum member order and ensure member names are not reused.
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EnumMeta will use the names found in self._member_names as the
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enumeration member names.
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"""
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def __init__(self):
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super().__init__()
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self._member_names = []
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def __setitem__(self, key, value):
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"""Changes anything not dundered or not a descriptor.
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If an enum member name is used twice, an error is raised; duplicate
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values are not checked for.
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Single underscore (sunder) names are reserved.
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"""
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if _is_sunder(key):
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raise ValueError('_names_ are reserved for future Enum use')
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elif _is_dunder(key):
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pass
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elif key in self._member_names:
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# descriptor overwriting an enum?
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raise TypeError('Attempted to reuse key: %r' % key)
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elif not _is_descriptor(value):
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if key in self:
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# enum overwriting a descriptor?
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raise TypeError('Key already defined as: %r' % self[key])
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self._member_names.append(key)
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super().__setitem__(key, value)
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# Dummy value for Enum as EnumMeta explicitly checks for it, but of course
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# until EnumMeta finishes running the first time the Enum class doesn't exist.
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# This is also why there are checks in EnumMeta like `if Enum is not None`
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Enum = None
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class EnumMeta(type):
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"""Metaclass for Enum"""
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@classmethod
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def __prepare__(metacls, cls, bases):
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return _EnumDict()
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def __new__(metacls, cls, bases, classdict):
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# an Enum class is final once enumeration items have been defined; it
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# cannot be mixed with other types (int, float, etc.) if it has an
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# inherited __new__ unless a new __new__ is defined (or the resulting
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# class will fail).
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member_type, first_enum = metacls._get_mixins_(bases)
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__new__, save_new, use_args = metacls._find_new_(classdict, member_type,
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first_enum)
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# save enum items into separate mapping so they don't get baked into
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# the new class
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members = {k: classdict[k] for k in classdict._member_names}
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for name in classdict._member_names:
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del classdict[name]
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# check for illegal enum names (any others?)
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invalid_names = set(members) & {'mro', }
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if invalid_names:
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raise ValueError('Invalid enum member name: {0}'.format(
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','.join(invalid_names)))
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# create our new Enum type
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enum_class = super().__new__(metacls, cls, bases, classdict)
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enum_class._member_names_ = [] # names in definition order
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enum_class._member_map_ = OrderedDict() # name->value map
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enum_class._member_type_ = member_type
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# save attributes from super classes so we know if we can take
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# the shortcut of storing members in the class dict
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base_attributes = {a for b in bases for a in b.__dict__}
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# Reverse value->name map for hashable values.
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enum_class._value2member_map_ = {}
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# If a custom type is mixed into the Enum, and it does not know how
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# to pickle itself, pickle.dumps will succeed but pickle.loads will
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# fail. Rather than have the error show up later and possibly far
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# from the source, sabotage the pickle protocol for this class so
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# that pickle.dumps also fails.
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#
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# However, if the new class implements its own __reduce_ex__, do not
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# sabotage -- it's on them to make sure it works correctly. We use
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# __reduce_ex__ instead of any of the others as it is preferred by
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# pickle over __reduce__, and it handles all pickle protocols.
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if '__reduce_ex__' not in classdict:
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if member_type is not object:
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methods = ('__getnewargs_ex__', '__getnewargs__',
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'__reduce_ex__', '__reduce__')
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if not any(m in member_type.__dict__ for m in methods):
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_make_class_unpicklable(enum_class)
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# instantiate them, checking for duplicates as we go
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# we instantiate first instead of checking for duplicates first in case
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# a custom __new__ is doing something funky with the values -- such as
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# auto-numbering ;)
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for member_name in classdict._member_names:
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value = members[member_name]
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if not isinstance(value, tuple):
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args = (value, )
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else:
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args = value
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if member_type is tuple: # special case for tuple enums
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args = (args, ) # wrap it one more time
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if not use_args:
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enum_member = __new__(enum_class)
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if not hasattr(enum_member, '_value_'):
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enum_member._value_ = value
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else:
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enum_member = __new__(enum_class, *args)
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if not hasattr(enum_member, '_value_'):
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enum_member._value_ = member_type(*args)
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value = enum_member._value_
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enum_member._name_ = member_name
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enum_member.__objclass__ = enum_class
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enum_member.__init__(*args)
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# If another member with the same value was already defined, the
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# new member becomes an alias to the existing one.
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for name, canonical_member in enum_class._member_map_.items():
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if canonical_member._value_ == enum_member._value_:
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enum_member = canonical_member
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break
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else:
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# Aliases don't appear in member names (only in __members__).
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enum_class._member_names_.append(member_name)
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# performance boost for any member that would not shadow
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# a DynamicClassAttribute
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if member_name not in base_attributes:
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setattr(enum_class, member_name, enum_member)
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# now add to _member_map_
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enum_class._member_map_[member_name] = enum_member
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try:
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# This may fail if value is not hashable. We can't add the value
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# to the map, and by-value lookups for this value will be
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# linear.
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enum_class._value2member_map_[value] = enum_member
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except TypeError:
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pass
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# double check that repr and friends are not the mixin's or various
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# things break (such as pickle)
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for name in ('__repr__', '__str__', '__format__', '__reduce_ex__'):
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class_method = getattr(enum_class, name)
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obj_method = getattr(member_type, name, None)
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enum_method = getattr(first_enum, name, None)
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if obj_method is not None and obj_method is class_method:
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setattr(enum_class, name, enum_method)
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# replace any other __new__ with our own (as long as Enum is not None,
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# anyway) -- again, this is to support pickle
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if Enum is not None:
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# if the user defined their own __new__, save it before it gets
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# clobbered in case they subclass later
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if save_new:
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enum_class.__new_member__ = __new__
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enum_class.__new__ = Enum.__new__
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return enum_class
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def __call__(cls, value, names=None, *, module=None, qualname=None, type=None, start=1):
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"""Either returns an existing member, or creates a new enum class.
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This method is used both when an enum class is given a value to match
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to an enumeration member (i.e. Color(3)) and for the functional API
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(i.e. Color = Enum('Color', names='red green blue')).
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When used for the functional API:
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`value` will be the name of the new class.
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`names` should be either a string of white-space/comma delimited names
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(values will start at `start`), or an iterator/mapping of name, value pairs.
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`module` should be set to the module this class is being created in;
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if it is not set, an attempt to find that module will be made, but if
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it fails the class will not be picklable.
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`qualname` should be set to the actual location this class can be found
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at in its module; by default it is set to the global scope. If this is
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not correct, unpickling will fail in some circumstances.
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`type`, if set, will be mixed in as the first base class.
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"""
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if names is None: # simple value lookup
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return cls.__new__(cls, value)
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# otherwise, functional API: we're creating a new Enum type
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return cls._create_(value, names, module=module, qualname=qualname, type=type, start=start)
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def __contains__(cls, member):
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return isinstance(member, cls) and member._name_ in cls._member_map_
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def __delattr__(cls, attr):
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# nicer error message when someone tries to delete an attribute
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# (see issue19025).
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if attr in cls._member_map_:
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raise AttributeError(
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"%s: cannot delete Enum member." % cls.__name__)
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super().__delattr__(attr)
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def __dir__(self):
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return (['__class__', '__doc__', '__members__', '__module__'] +
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self._member_names_)
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def __getattr__(cls, name):
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"""Return the enum member matching `name`
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We use __getattr__ instead of descriptors or inserting into the enum
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class' __dict__ in order to support `name` and `value` being both
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properties for enum members (which live in the class' __dict__) and
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enum members themselves.
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"""
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if _is_dunder(name):
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raise AttributeError(name)
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try:
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return cls._member_map_[name]
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except KeyError:
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raise AttributeError(name) from None
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def __getitem__(cls, name):
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return cls._member_map_[name]
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def __iter__(cls):
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return (cls._member_map_[name] for name in cls._member_names_)
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def __len__(cls):
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return len(cls._member_names_)
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@property
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def __members__(cls):
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"""Returns a mapping of member name->value.
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This mapping lists all enum members, including aliases. Note that this
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is a read-only view of the internal mapping.
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"""
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return MappingProxyType(cls._member_map_)
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def __repr__(cls):
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return "<enum %r>" % cls.__name__
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def __reversed__(cls):
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return (cls._member_map_[name] for name in reversed(cls._member_names_))
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def __setattr__(cls, name, value):
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"""Block attempts to reassign Enum members.
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A simple assignment to the class namespace only changes one of the
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several possible ways to get an Enum member from the Enum class,
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resulting in an inconsistent Enumeration.
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"""
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member_map = cls.__dict__.get('_member_map_', {})
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if name in member_map:
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raise AttributeError('Cannot reassign members.')
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super().__setattr__(name, value)
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def _create_(cls, class_name, names=None, *, module=None, qualname=None, type=None, start=1):
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"""Convenience method to create a new Enum class.
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`names` can be:
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* A string containing member names, separated either with spaces or
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commas. Values are incremented by 1 from `start`.
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* An iterable of member names. Values are incremented by 1 from `start`.
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* An iterable of (member name, value) pairs.
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* A mapping of member name -> value pairs.
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"""
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metacls = cls.__class__
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bases = (cls, ) if type is None else (type, cls)
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classdict = metacls.__prepare__(class_name, bases)
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# special processing needed for names?
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if isinstance(names, str):
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names = names.replace(',', ' ').split()
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if isinstance(names, (tuple, list)) and isinstance(names[0], str):
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names = [(e, i) for (i, e) in enumerate(names, start)]
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# Here, names is either an iterable of (name, value) or a mapping.
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for item in names:
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if isinstance(item, str):
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member_name, member_value = item, names[item]
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else:
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member_name, member_value = item
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classdict[member_name] = member_value
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enum_class = metacls.__new__(metacls, class_name, bases, classdict)
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# TODO: replace the frame hack if a blessed way to know the calling
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# module is ever developed
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if module is None:
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try:
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module = sys._getframe(2).f_globals['__name__']
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except (AttributeError, ValueError) as exc:
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pass
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if module is None:
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_make_class_unpicklable(enum_class)
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else:
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enum_class.__module__ = module
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if qualname is not None:
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enum_class.__qualname__ = qualname
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return enum_class
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@staticmethod
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def _get_mixins_(bases):
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"""Returns the type for creating enum members, and the first inherited
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enum class.
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bases: the tuple of bases that was given to __new__
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"""
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if not bases:
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return object, Enum
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# double check that we are not subclassing a class with existing
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# enumeration members; while we're at it, see if any other data
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# type has been mixed in so we can use the correct __new__
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member_type = first_enum = None
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for base in bases:
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if (base is not Enum and
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issubclass(base, Enum) and
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base._member_names_):
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raise TypeError("Cannot extend enumerations")
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# base is now the last base in bases
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if not issubclass(base, Enum):
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raise TypeError("new enumerations must be created as "
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"`ClassName([mixin_type,] enum_type)`")
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# get correct mix-in type (either mix-in type of Enum subclass, or
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# first base if last base is Enum)
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if not issubclass(bases[0], Enum):
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member_type = bases[0] # first data type
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first_enum = bases[-1] # enum type
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else:
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for base in bases[0].__mro__:
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# most common: (IntEnum, int, Enum, object)
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# possible: (<Enum 'AutoIntEnum'>, <Enum 'IntEnum'>,
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# <class 'int'>, <Enum 'Enum'>,
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# <class 'object'>)
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if issubclass(base, Enum):
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if first_enum is None:
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first_enum = base
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else:
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if member_type is None:
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member_type = base
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return member_type, first_enum
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@staticmethod
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def _find_new_(classdict, member_type, first_enum):
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"""Returns the __new__ to be used for creating the enum members.
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classdict: the class dictionary given to __new__
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member_type: the data type whose __new__ will be used by default
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first_enum: enumeration to check for an overriding __new__
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"""
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# now find the correct __new__, checking to see of one was defined
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# by the user; also check earlier enum classes in case a __new__ was
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# saved as __new_member__
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__new__ = classdict.get('__new__', None)
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# should __new__ be saved as __new_member__ later?
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save_new = __new__ is not None
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if __new__ is None:
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# check all possibles for __new_member__ before falling back to
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# __new__
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for method in ('__new_member__', '__new__'):
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for possible in (member_type, first_enum):
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target = getattr(possible, method, None)
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if target not in {
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None,
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None.__new__,
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object.__new__,
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Enum.__new__,
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}:
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__new__ = target
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break
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if __new__ is not None:
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break
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else:
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__new__ = object.__new__
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# if a non-object.__new__ is used then whatever value/tuple was
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# assigned to the enum member name will be passed to __new__ and to the
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# new enum member's __init__
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if __new__ is object.__new__:
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use_args = False
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else:
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use_args = True
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return __new__, save_new, use_args
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class Enum(metaclass=EnumMeta):
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"""Generic enumeration.
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Derive from this class to define new enumerations.
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"""
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def __new__(cls, value):
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# all enum instances are actually created during class construction
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# without calling this method; this method is called by the metaclass'
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# __call__ (i.e. Color(3) ), and by pickle
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if type(value) is cls:
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# For lookups like Color(Color.red)
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return value
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# by-value search for a matching enum member
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# see if it's in the reverse mapping (for hashable values)
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try:
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if value in cls._value2member_map_:
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return cls._value2member_map_[value]
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except TypeError:
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# not there, now do long search -- O(n) behavior
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for member in cls._member_map_.values():
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if member._value_ == value:
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return member
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raise ValueError("%r is not a valid %s" % (value, cls.__name__))
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def __repr__(self):
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return "<%s.%s: %r>" % (
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self.__class__.__name__, self._name_, self._value_)
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def __str__(self):
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return "%s.%s" % (self.__class__.__name__, self._name_)
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def __dir__(self):
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added_behavior = [
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m
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for cls in self.__class__.mro()
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for m in cls.__dict__
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if m[0] != '_' and m not in self._member_map_
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]
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return (['__class__', '__doc__', '__module__'] + added_behavior)
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def __format__(self, format_spec):
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# mixed-in Enums should use the mixed-in type's __format__, otherwise
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# we can get strange results with the Enum name showing up instead of
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# the value
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# pure Enum branch
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if self._member_type_ is object:
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cls = str
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val = str(self)
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# mix-in branch
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else:
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cls = self._member_type_
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val = self._value_
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return cls.__format__(val, format_spec)
|
|
|
|
def __hash__(self):
|
|
return hash(self._name_)
|
|
|
|
def __reduce_ex__(self, proto):
|
|
return self.__class__, (self._value_, )
|
|
|
|
# DynamicClassAttribute is used to provide access to the `name` and
|
|
# `value` properties of enum members while keeping some measure of
|
|
# protection from modification, while still allowing for an enumeration
|
|
# to have members named `name` and `value`. This works because enumeration
|
|
# members are not set directly on the enum class -- __getattr__ is
|
|
# used to look them up.
|
|
|
|
@DynamicClassAttribute
|
|
def name(self):
|
|
"""The name of the Enum member."""
|
|
return self._name_
|
|
|
|
@DynamicClassAttribute
|
|
def value(self):
|
|
"""The value of the Enum member."""
|
|
return self._value_
|
|
|
|
@classmethod
|
|
def _convert(cls, name, module, filter, source=None):
|
|
"""
|
|
Create a new Enum subclass that replaces a collection of global constants
|
|
"""
|
|
# convert all constants from source (or module) that pass filter() to
|
|
# a new Enum called name, and export the enum and its members back to
|
|
# module;
|
|
# also, replace the __reduce_ex__ method so unpickling works in
|
|
# previous Python versions
|
|
module_globals = vars(sys.modules[module])
|
|
if source:
|
|
source = vars(source)
|
|
else:
|
|
source = module_globals
|
|
members = {name: value for name, value in source.items()
|
|
if filter(name)}
|
|
cls = cls(name, members, module=module)
|
|
cls.__reduce_ex__ = _reduce_ex_by_name
|
|
module_globals.update(cls.__members__)
|
|
module_globals[name] = cls
|
|
return cls
|
|
|
|
|
|
class IntEnum(int, Enum):
|
|
"""Enum where members are also (and must be) ints"""
|
|
|
|
|
|
def _reduce_ex_by_name(self, proto):
|
|
return self.name
|
|
|
|
def unique(enumeration):
|
|
"""Class decorator for enumerations ensuring unique member values."""
|
|
duplicates = []
|
|
for name, member in enumeration.__members__.items():
|
|
if name != member.name:
|
|
duplicates.append((name, member.name))
|
|
if duplicates:
|
|
alias_details = ', '.join(
|
|
["%s -> %s" % (alias, name) for (alias, name) in duplicates])
|
|
raise ValueError('duplicate values found in %r: %s' %
|
|
(enumeration, alias_details))
|
|
return enumeration
|