Case insensitive dictionary

Question

Hi,

I'd like my dictionary to be case insensitive.

I have this example code:

text = "practice changing the color"

words = {'color': 'colour',
        'practice': 'practise'}

def replace(words,text):

    keys = words.keys()

    for i in keys:
        text= text.replace(i ,words[i])
    return  text

text = replace(words,text)

print text

Output = practise changing the colour

I'd like another string "practice changing the Color" (where 'Color' starts with a capital) to also give the same output.

I believe there is a general way to convert to lowercase using mydictionary[key.lower()] but I'm not sure how to best integrate this into my existing code. (If this would be a reasonable, simple approach anyway)

Could anyone help me please?

thanks

Answer 1

If I understand you correctly and you want a way to key dictionaries in a non case-sensitive fashion, one way would be to subclass dict and overload the setter / getter:

class CaseInsensitiveDict(dict):
    def __setitem__(self, key, value):
        super(CaseInsensitiveDict, self).__setitem__(key.lower(), value)

    def __getitem__(self, key):
        return super(CaseInsensitiveDict, self).__getitem__(key.lower())

Answer 2

have a look at this question http://stackoverflow.com/questions/919056/python-case-insensitive-replace

Answer 3

http://code.activestate.com/recipes/66315/

Answer 4

While a case insensitive dictionary is a solution, and there are answers to how to achieve that, there is a possibly easier way in this case. A case insensitive search is sufficient:

import re

text = "Practice changing the Color"
words = {'color': 'colour', 'practice': 'practise'}

def replace(words,text):
        keys = words.keys()
        for i in keys:
                exp = re.compile(i, re.I)
                text = re.sub(exp, words[i], text)
        return text

text = replace(words,text)
print text

Answer 5

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

Answer 6

Kim seems to have picked the regex-based solution from calmh because it was the one that was the most fully fleshed out (i.e. required the least understanding, just cut and paste the code). The subclass approach mentioned in other answers is more robust, but is probably too advanced for Kim. (No offense meant to Kim, we were all beginners once.)

inspectorG4dget's approach is the right level, but he didn't post code, so here it is:

text = "Practice changing the Color"
words = {'color': 'colour', 'practice': 'practise'}

def replace(words, text):
    keys = words.keys()
    text = text.lower()
    for i in keys:
        text = text.replace(i, words[i])
    return text

text = replace(words, text)
print text

Edit: calmh's comment was correct; my original code didn't work. I've changed (and tested!) what's above.

Note that I tried to stay close to Kim's posted code. It could be written more concisely, and with (I feel) better names, but one of the goals of this answer was to be as understandable and recognizable to Kim as possible.