字典与Python的反向映射 [英] reverse mapping of dictionary with Python

问题描述

可能重复：

反词典查找 - Python

如果我有一个名为ref的字典如下

If I have a dictionary named ref as follows

ref = {}
ref["abc"] = "def"

我可以从abc获得def

I can get "def" from "abc"

def mapper(from):
    return ref[from]

但是，如何从def到abc？

But, how can I get from "def" to "abc"?

def revmapper(to):
    ??????

推荐答案

如果经常这样做，构建一个反向字典：

If you do this often, you'll want to build a reverse dictionary:

>>> rev_ref = dict((v,k) for k,v in ref.iteritems())
>>> rev_ref
{'def': 'abc'}

>>> def revmapper(to):
...    return rev_ref[to]

如果很少，而且你不在乎它是否没有效率，请执行以下操作：

If it's rare, and you don't care if it's inefficient, do this:

>>> def revmapper(to):
...    for k,v in ref.iteritems():
...      if v == to: return k

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