Case insensitive dictionary

Question

I\'d like my dictionary to be case insensitive.

I have this example code:

text = \"practice changing the color\"

words = {\'color\': \'colour\',
            


        

Answer 1

I've modified the simple yet good solution by pleasemorebacon (thanks!) making it slightly more compact, self-contained and with minor updates to allow construction from {'a':1, 'B':2} and support __contains__ protocol. Finally, since the CaseInsensitiveDict.Key is expected to be string (what else can be case-sensitive or not), it is a good idea to derive Key class from the str, then it is possible, for instance, to dump CaseInsensitiveDict with json.dumps out of the box.

# caseinsensitivedict.py
class CaseInsensitiveDict(dict):

    class Key(str):
        def __init__(self, key):
            str.__init__(key)
        def __hash__(self):
            return hash(self.lower())
        def __eq__(self, other):
            return self.lower() == other.lower()

    def __init__(self, data=None):
        super(CaseInsensitiveDict, self).__init__()
        if data is None:
            data = {}
        for key, val in data.items():
            self[key] = val
    def __contains__(self, key):
        key = self.Key(key)
        return super(CaseInsensitiveDict, self).__contains__(key)
    def __setitem__(self, key, value):
        key = self.Key(key)
        super(CaseInsensitiveDict, self).__setitem__(key, value)
    def __getitem__(self, key):
        key = self.Key(key)
        return super(CaseInsensitiveDict, self).__getitem__(key)

Here is a basic test script for those who like to check things in action:

# test_CaseInsensitiveDict.py
import json
import unittest
from caseinsensitivedict import *

class Key(unittest.TestCase):
    def setUp(self):
        self.Key = CaseInsensitiveDict.Key
        self.lower = self.Key('a')
        self.upper = self.Key('A')

    def test_eq(self):
        self.assertEqual(self.lower, self.upper)

    def test_hash(self):
        self.assertEqual(hash(self.lower), hash(self.upper))

    def test_str(self):
        self.assertEqual(str(self.lower), 'a')
        self.assertEqual(str(self.upper), 'A')

class Dict(unittest.TestCase):
    def setUp(self):
        self.Dict = CaseInsensitiveDict
        self.d1 = self.Dict()
        self.d2 = self.Dict()
        self.d1['a'] = 1
        self.d1['B'] = 2
        self.d2['A'] = 1
        self.d2['b'] = 2

    def test_contains(self):
        self.assertIn('B', self.d1)
        d = self.Dict({'a':1, 'B':2})
        self.assertIn('b', d)

    def test_init(self):
        d = self.Dict()
        self.assertFalse(d)
        d = self.Dict({'a':1, 'B':2})
        self.assertTrue(d)

    def test_items(self):
        self.assertDictEqual(self.d1, self.d2)
        self.assertEqual(
            [v for v in self.d1.items()],
            [v for v in self.d2.items()])

    def test_json_dumps(self):
        s = json.dumps(self.d1)
        self.assertIn('a', s)
        self.assertIn('B', s)

    def test_keys(self):
        self.assertEqual(self.d1.keys(), self.d2.keys())

    def test_values(self):
        self.assertEqual(
            [v for v in self.d1.values()],
            [v for v in self.d2.values()])