运行命令pip2.7 show enum34输出版本和正确安装的位置：
Name: enum34
Version: 1.1.2
Summary: Python 3.4 Enum backported to 3.3, 3.2, 3.1, 2.7, 2.6, 2.5, and 2.4
Home-page: https://pypi.python.org/pypi/enum34
Author: Ethan Furman
Author-email: ethan@stoneleaf.us
License: BSD License
Location: /usr/lib/python2.7/dist-packages
Requires:
Required-by:
尽管如此，我在enum上遇到以下错误：
AttributeError: 'enum' object has no attribute 'IntFlag'
如果您没有在enum34中安装python 2.7，但已经安装了该错误，则会发生此错误。
我可以导入enum并运行enum.__file__输出路径：
/usr/lib/python2.7/dist-packages/enum/__init__.pyc
IntFlag，为什么enum中缺少enum34？答案 0 :(得分：1)
如果您查看Wix MajorUpgrade problems的文档，则会发现IntFlag不存在。那是因为它是3.4 enum。
因此，您看到的错误确实是正确的，而不是enum34安装的问题。
看起来pypi中的enum软件包也没有IntFlag。
您可以通过复制added in 3.6的源代码来轻松地对此补丁进行猴子修补：
from enum import Enum
class Flag(Enum):
"""Support for flags"""
def _generate_next_value_(name, start, count, last_values):
"""
Generate the next value when not given.
name: the name of the member
start: the initital start value or None
count: the number of existing members
last_value: the last value assigned or None
"""
if not count:
return start if start is not None else 1
for last_value in reversed(last_values):
try:
high_bit = _high_bit(last_value)
break
except Exception:
raise TypeError('Invalid Flag value: %r' % last_value) from None
return 2 ** (high_bit+1)
@classmethod
def _missing_(cls, value):
original_value = value
if value < 0:
value = ~value
possible_member = cls._create_pseudo_member_(value)
if original_value < 0:
possible_member = ~possible_member
return possible_member
@classmethod
def _create_pseudo_member_(cls, value):
"""
Create a composite member iff value contains only members.
"""
pseudo_member = cls._value2member_map_.get(value, None)
if pseudo_member is None:
# verify all bits are accounted for
_, extra_flags = _decompose(cls, value)
if extra_flags:
raise ValueError("%r is not a valid %s" % (value, cls.__name__))
# construct a singleton enum pseudo-member
pseudo_member = object.__new__(cls)
pseudo_member._name_ = None
pseudo_member._value_ = value
# use setdefault in case another thread already created a composite
# with this value
pseudo_member = cls._value2member_map_.setdefault(value, pseudo_member)
return pseudo_member
def __contains__(self, other):
if not isinstance(other, self.__class__):
import warnings
warnings.warn(
"using non-Flags in containment checks will raise "
"TypeError in Python 3.8",
DeprecationWarning, 2)
return False
return other._value_ & self._value_ == other._value_
def __repr__(self):
cls = self.__class__
if self._name_ is not None:
return '<%s.%s: %r>' % (cls.__name__, self._name_, self._value_)
members, uncovered = _decompose(cls, self._value_)
return '<%s.%s: %r>' % (
cls.__name__,
'|'.join([str(m._name_ or m._value_) for m in members]),
self._value_,
)
def __str__(self):
cls = self.__class__
if self._name_ is not None:
return '%s.%s' % (cls.__name__, self._name_)
members, uncovered = _decompose(cls, self._value_)
if len(members) == 1 and members[0]._name_ is None:
return '%s.%r' % (cls.__name__, members[0]._value_)
else:
return '%s.%s' % (
cls.__name__,
'|'.join([str(m._name_ or m._value_) for m in members]),
)
def __bool__(self):
return bool(self._value_)
def __or__(self, other):
if not isinstance(other, self.__class__):
return NotImplemented
return self.__class__(self._value_ | other._value_)
def __and__(self, other):
if not isinstance(other, self.__class__):
return NotImplemented
return self.__class__(self._value_ & other._value_)
def __xor__(self, other):
if not isinstance(other, self.__class__):
return NotImplemented
return self.__class__(self._value_ ^ other._value_)
def __invert__(self):
members, uncovered = _decompose(self.__class__, self._value_)
inverted = self.__class__(0)
for m in self.__class__:
if m not in members and not (m._value_ & self._value_):
inverted = inverted | m
return self.__class__(inverted)
class IntFlag(int, Flag):
"""Support for integer-based Flags"""
@classmethod
def _missing_(cls, value):
if not isinstance(value, int):
raise ValueError("%r is not a valid %s" % (value, cls.__name__))
new_member = cls._create_pseudo_member_(value)
return new_member
@classmethod
def _create_pseudo_member_(cls, value):
pseudo_member = cls._value2member_map_.get(value, None)
if pseudo_member is None:
need_to_create = [value]
# get unaccounted for bits
_, extra_flags = _decompose(cls, value)
# timer = 10
while extra_flags:
# timer -= 1
bit = _high_bit(extra_flags)
flag_value = 2 ** bit
if (flag_value not in cls._value2member_map_ and
flag_value not in need_to_create
):
need_to_create.append(flag_value)
if extra_flags == -flag_value:
extra_flags = 0
else:
extra_flags ^= flag_value
for value in reversed(need_to_create):
# construct singleton pseudo-members
pseudo_member = int.__new__(cls, value)
pseudo_member._name_ = None
pseudo_member._value_ = value
# use setdefault in case another thread already created a composite
# with this value
pseudo_member = cls._value2member_map_.setdefault(value, pseudo_member)
return pseudo_member
def __or__(self, other):
if not isinstance(other, (self.__class__, int)):
return NotImplemented
result = self.__class__(self._value_ | self.__class__(other)._value_)
return result
def __and__(self, other):
if not isinstance(other, (self.__class__, int)):
return NotImplemented
return self.__class__(self._value_ & self.__class__(other)._value_)
def __xor__(self, other):
if not isinstance(other, (self.__class__, int)):
return NotImplemented
return self.__class__(self._value_ ^ self.__class__(other)._value_)
__ror__ = __or__
__rand__ = __and__
__rxor__ = __xor__
def __invert__(self):
result = self.__class__(~self._value_)
return result
def _high_bit(value):
"""returns index of highest bit, or -1 if value is zero or negative"""
return value.bit_length() - 1
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
def _decompose(flag, value):
"""Extract all members from the value."""
# _decompose is only called if the value is not named
not_covered = value
negative = value < 0
# issue29167: wrap accesses to _value2member_map_ in a list to avoid race
# conditions between iterating over it and having more pseudo-
# members added to it
if negative:
# only check for named flags
flags_to_check = [
(m, v)
for v, m in list(flag._value2member_map_.items())
if m.name is not None
]
else:
# check for named flags and powers-of-two flags
flags_to_check = [
(m, v)
for v, m in list(flag._value2member_map_.items())
if m.name is not None or _power_of_two(v)
]
members = []
for member, member_value in flags_to_check:
if member_value and member_value & value == member_value:
members.append(member)
not_covered &= ~member_value
if not members and value in flag._value2member_map_:
members.append(flag._value2member_map_[value])
members.sort(key=lambda m: m._value_, reverse=True)
if len(members) > 1 and members[0].value == value:
# we have the breakdown, don't need the value member itself
members.pop(0)
return members, not_covered
def _power_of_two(value):
if value < 1:
return False
return value == 2 ** _high_bit(value)
尽管如此，您最好将整个模块复制到自己的模块中（这样就不必依赖方法中未记录的内容了）。
进一步@ user2357112提到，您所看到的错误表明您可能不小心覆盖了代码中的枚举模块。请注意，由于您为名称sys分配了不同于导入模块的其他值，因此类似的事情将会中断：
import sys
sys = 1 # doesn't have to be 1, can be anything that's not sys
# sys is no longer the module you imported, this will fail
sys.stdout.write('hello world!\n')
我怀疑您的代码中您可能正在执行以下操作：
import enum
class Foo(enum.Enum):
BAR = 1
enum = Foo.Bar # or something like this
class Baz(enum.Enum): # failure happens here, enum is now Foo.Bar
pass