enum34未正确安装Python 2.7

Question

运行命令pip2.7 show enum34输出正确安装的版本和位置：

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: 

但是，我在enum中出现以下错误：

^{pr2}$

当您没有在python 2.7中安装enum34，但它已经安装时，就会发生此错误。在

我可以导入enum并运行enum.__file__输出路径：

/usr/lib/python2.7/dist-packages/enum/__init__.pyc

• 如果安装了enum34，为什么IntFlag在{}中丢失？在

Answer 1

如果您查看3.4 ^{}的文档，就会发现{}不在那里。那是因为它是added in 3.6。在

因此，您看到的错误确实是正确的，enum34安装没有问题。在

看起来pypi中的enum包也没有IntFlag。在

通过复制^{} into a module in your project的源代码，您可以很容易地修补此问题：

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)

不过，最好将整个模块复制到自己的模块中（这样就不会依赖于方法下的未文档化）。在

此外，正如@user2357112所提到的，您看到的错误表明您可能意外地覆盖了代码中的enum模块。为了清楚起见，类似这样的情况会中断，因为您已经为名称sys分配了其他值，而不是导入的模块：

^{pr2}$

我怀疑在你的代码里你可能在做这样的事情：

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