不区分大小写的词典搜索? [英] Case insensitive dictionary search?

问题描述

我可以使用map使用Python来实现不区分大小写的列表搜索.

a = ['xyz', 'wMa', 'Pma'];

b = map(string.lower, a)
if 'Xyz'.lower() in b:
    print 'yes'

如何用字典做同样的事情?

我尝试了以下代码，但是ap具有['a'，'b'，'c']的列表，而不区分大小写的字典.

a = {'a':1, 'B':2, 'c':3}
ap = map(string.lower, a)

解决方案

请注意，使字典不区分大小写，无论采用何种方式，都可能会丢失信息:例如，您将如何不区分大小写" {'a': 23, 'A': 45}? ！如果您只关心键中是否存在键(即，不在乎与之对应的值)，则改为使用set，即

theset = set(k.lower() for k in thedict)

(在每个Python版本中，或{k.lower() for k in thedict}，如果您对只在Python 2.7或更高版本中运行的代码感到满意，则出于某种纯粹的装饰性语法糖；-)，并使用if k.lower() in theset: ...进行检查. /p>

或者，您可以创建一个包装器类，例如，一个只读类...:

import collections

class CaseInsensitiveDict(collections.Mapping):
    def __init__(self, d):
        self._d = d
        self._s = dict((k.lower(), k) for k in d)
    def __contains__(self, k):
        return k.lower() in self._s
    def __len__(self):
        return len(self._s)
    def __iter__(self):
        return iter(self._s)
    def __getitem__(self, k):
        return self._d[self._s[k.lower()]]
    def actual_key_case(self, k):
        return self._s.get(k.lower())

这将保留(实际上并不需要更改原始词典，因此，如果需要的话，仍然可以为它检索所有精确的信息)键的可能多个值中的任意一个，这些键由于以下原因折叠"为单个键:不区分大小写，并提供字典的所有只读方法(仅带字符串键)以及actual_key_case方法，该方法返回用于任何给定字符串键的实际大小写混合(如果没有大小写更改，则返回None给定的字符串键匹配字典中的任何键.

I can use map to implement the case insensitive list search with Python.

a = ['xyz', 'wMa', 'Pma'];

b = map(string.lower, a)
if 'Xyz'.lower() in b:
    print 'yes'

How can I do the same thing with dictionary?

I tried the following code, but ap has the list of ['a','b','c'], not the case insensitive dictionary.

a = {'a':1, 'B':2, 'c':3}
ap = map(string.lower, a)

解决方案

Note that making a dictionary case-insensitive, by whatever mean, may well lose information: for example, how would you "case-insensitivize" {'a': 23, 'A': 45}?! If all you care is where a key is in the dict or not (i.e., don't care about what value corresponds to it), then make a set instead -- i.e.

theset = set(k.lower() for k in thedict)

(in every version of Python, or {k.lower() for k in thedict} if you're happy with your code working only in Python 2.7 or later for the sake of some purely decorative syntax sugar;-), and check with if k.lower() in theset: ....

Or, you could make a wrapper class, e.g., maybe a read-only one...:

import collections

class CaseInsensitiveDict(collections.Mapping):
    def __init__(self, d):
        self._d = d
        self._s = dict((k.lower(), k) for k in d)
    def __contains__(self, k):
        return k.lower() in self._s
    def __len__(self):
        return len(self._s)
    def __iter__(self):
        return iter(self._s)
    def __getitem__(self, k):
        return self._d[self._s[k.lower()]]
    def actual_key_case(self, k):
        return self._s.get(k.lower())

This will keep (without actually altering the original dictionary, so all precise information can still be retrieve for it, if and when needed) an arbitrary one of possibly-multiple values for keys that "collapse" into a single key due to the case-insensitiveness, and offer all read-only methods of dictionaries (with string keys, only) plus an actual_key_case method returning the actual case mix used for any given string key (or None if no case-alteration of that given string key matches any key in the dictionary).

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