Question

我目前需要一个类似于内置dict类型的类似功能的Python容器类。基本上我需要的是一个字典，其中主键旁边的任意数量的键，映射到相同的值。但是，当迭代它时，它应该仅在(primary_key, value)对上迭代，如果请求键列表，则仅迭代主键。

如果这已经实施，我宁愿不重新发明轮子。那么是否有一个模块提供这样的容器？如果没有，我将自己实施。

Answer 1

这是一个快速实施：

class MultipleKeyDict(dict):
    __slots__ = ["_primary_keys"]
    def __init__(self, arg=None, **kwargs):
        self._primary_keys = {}
        self.update(arg, **kwargs)
    def __setitem__(self, key, value):
        super(MultipleKeyDict, self).__setitem__(key, value)
        self._primary_keys.setdefault(value, key)
    def __delitem__(self, key):
        value = self[key]
        super(MultipleKeyDict, self).__delitem__(key)
        if self._primary_keys[value] == key:
            del self._primary_keys[value]
            for k, v in super(MultipleKeyDict, self).iteritems():
                if v == value:
                    self._primary_keys[value] = k
                    break
    def __iter__(self):
        return self.iterkeys()
    def update(self, arg=None, **kwargs):
        if arg is not None:
            if isinstance(arg, collections.Mapping):
                for k in arg:
                    self[k] = arg[k]
            else:
                for k, v in arg:
                    self[k] = v
        for k in kwargs:
            self[k] = kwargs[k]
    def clear(self):
        super(MultipleKeyDict, self).clear()
        self._primary_keys.clear()
    def iteritems(self):
        for v, k in self._primary_keys.iteritems():
            yield k, v
    def items(self):
        return list(self.iteritems())
    def itervalues(self):
        return self._primary_keys.iterkeys()
    def values(self):
        return self._primary_keys.keys()
    def iterkeys(self):
        return self._primary_keys.itervalues()
    def keys(self):
        return self._primary_keys.values()

唯一令人讨厌的一点是它必须搜索整个dict以防主键被删除。

我省略了copy()，pop()，popitem()和setdefault()。如果你需要它们，你必须自己实现它们。

Answer 2

最简单和最简单的解决方案是使用两个词典，其中一个将辅助键映射到主键。如果由于某种原因需要反向映射，则可以将其包含在主字典中。

sec = {'one': 'blue', 'two': 'red', 'three': 'blue',   # seconary keys
       'blue': 'blue', 'red': 'red'}                   # include identity mapping for primaries
dict = {'blue': ('doll', '$9.43', ('one', 'three')),
        'red':  ('truck', '$14.99', ('two',)) }

record = dict[sec['two']]
print('Toy=', record[0], 'Price=', record[1])

Answer 3

现在有一个多关键字典python包。
https://pypi.python.org/pypi/multi_key_dict/1.0.2

从链接：

from multi_key_dict import multi_key_dict

k = multi_key_dict()
k[1000, 'kilo', 'k'] = 'kilo (x1000)'

print k[1000] # will print 'kilo (x1000)'
print k['k'] # will also print 'kilo (x1000)'

# the same way objects can be updated, deleted:
# and if an object is updated using one key, the new value will
# be accessible using any other key, e.g. for example above:
k['kilo'] = 'kilo'
print k[1000] # will now print 'kilo' as value was updated

Python dict喜欢surjective multiple key→value container

3 个答案: