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

You can do a dict key case insensitive search with a one liner:

>>> input_dict = {'aBc':1, 'xyZ':2}
>>> search_string = 'ABC'
>>> next((value for key, value in input_dict.items() if key.lower()==search_string.lower()), None)
1
>>> search_string = 'EFG'
>>> next((value for key, value in input_dict.items() if key.lower()==search_string.lower()), None)
>>>

You can place that into a function:

def get_case_insensitive_key_value(input_dict, key):
    return next((value for dict_key, value in input_dict.items() if dict_key.lower() == key.lower()), None)

Note that only the first match is returned.

Answer 2

If you only need to do this once in your code (hence, no point to a function), the most straightforward way to deal with the problem is this:

lowercase_dict = {key.lower(): value for (key, value) in original_dict}

I'm assuming here that the dict in question isn't all that large--it might be inelegant to duplicate it, but if it's not large, it isn't going to hurt anything.

The advantage of this over @Fred's answer (though that also works) is that it produces the same result as a dict when the key isn't present: a KeyError.

Answer 3

I just set up a function to handle this:

def setLCdict(d, k, v):
    k = k.lower()
    d[k] = v
    return d

myDict = {}

So instead of

myDict['A'] = 1
myDict['B'] = 2

You can:

myDict = setLCdict(myDict, 'A', 1)
myDict = setLCdict(myDict, 'B', 2)

You can then either lower case the value before looking it up or write a function to do so.

    def lookupLCdict(d, k):
        k = k.lower()
        return d[k]

    myVal = lookupLCdict(myDict, 'a')

Probably not ideal if you want to do this globally but works well if its just a subset you wish to use it for.

Answer 4

Would you consider using string.lower() on your inputs and using a fully lowercase dictionary? It's a bit of a hacky solution, but it works