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In Python 3, I'd like to be able to use re.sub() in an "accent-insensitive" way, as we can do with the re.I flag for case-insensitive substitution.

Could be something like a re.IGNOREACCENTS flag:

original_text = "¿It's 80°C, I'm drinking a café in a cafe with Chloë。" accent_regex = r'a café' re.sub(accent_regex, 'X', original_text, flags=re.IGNOREACCENTS)

This would lead to "¿It's 80°C, I'm drinking X in X with Chloë。" (note that there's still an accent on "Chloë") instead of "¿It's 80°C, I'm drinking X in a cafe with Chloë。" in real python.

I think that such a flag doesn't exist. So what would be the best option to do this? Using re.finditer and unidecode on both original_text and accent_regex and then replace by splitting the string? Or modifying all characters in the accent_regex by their accented variants, for instance: r'[cç][aàâ]f[éèêë]'?

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  • 1
    Could be something like... @WiktorStribiżew Commented Apr 26, 2017 at 12:45
  • What you are looking for is a equivalence class - though I don't know any python regex module that supports them. Syntax is usually like [[=a=]] Commented Apr 26, 2017 at 12:51

3 Answers 3

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unidecode is often mentioned for removing accents in Python, but it also does more than that : it converts '°' to 'deg', which might not be the desired output.

unicodedata seems to have enough functionality to remove accents.

With any pattern

This method should work with any pattern and any text.

You can temporarily remove the accents from both the text and regex pattern. The match information from re.finditer() (start and end indices) can be used to modify the original, accented text.

Note that the matches must be reversed in order to not modify the following indices.

import re import unicodedata original_text = "I'm drinking a 80° café in a cafe with Chloë, François Déporte and Francois Deporte." accented_pattern = r'a café|François Déporte' def remove_accents(s): return ''.join((c for c in unicodedata.normalize('NFD', s) if unicodedata.category(c) != 'Mn')) print(remove_accents('äöüßéèiìììíàáç')) # aoußeeiiiiiaac pattern = re.compile(remove_accents(accented_pattern)) modified_text = original_text matches = list(re.finditer(pattern, remove_accents(original_text))) for match in matches[::-1]: modified_text = modified_text[:match.start()] + 'X' + modified_text[match.end():] print(modified_text) # I'm drinking a 80° café in X with Chloë, X and X.

If pattern is a word or a set of words

You could :

  • remove the accents out of your pattern words and save them in a set for fast lookup
  • look for every word in your text with \w+
  • remove the accents from the word:
    • If it matches, replace by X
    • If it doesn't match, leave the word untouched
import re from unidecode import unidecode original_text = "I'm drinking a café in a cafe with Chloë." def remove_accents(string): return unidecode(string) accented_words = ['café', 'français'] words_to_remove = set(remove_accents(word) for word in accented_words) def remove_words(matchobj): word = matchobj.group(0) if remove_accents(word) in words_to_remove: return 'X' else: return word print(re.sub('\w+', remove_words, original_text)) # I'm drinking a X in a X with Chloë.
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11 Comments

Thanks, this method is smart! How to modify it to replace not only words but also n-gram? (I edited my question to take this option into account, for instance to replace "François Déporte" in a text where only "Francois Deporte" appears)
@AntoineDusséaux: No problem, the first method works fine.
Smart! I tried everything to break your solution and it seems it doesn't work with 'string_to_change = 'äöüßéèiìììíàáç°。阿bcqf反題梓z≤«»Ωfiñ한か¿？！'' ;) so I changed it a little bit: return ''.join((unidecode.unidecode(c) if len(unidecode.unidecode(c)) == len(c) else c for c in s)) and it seems to work fine!
@AntoineDusséaux: Unicode can be so complex that it's pretty easy to break any code with it.
To avoid this we could escape all characters: return ''.join(re.escape(unidecode.unidecode(c)) if len(unidecode.unidecode(c)) == len(c) else re.escape(c) for c in s) (tested with string_to_change = 'äöüßéèiìììíàáç°。阿bcqf反題梓z≤«»Ωfiñ한か¿⸼？！..·⁂‖¦•+⸮…')
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You can use Unidecode:

$ pip install unidecode

In your program:

from unidecode import unidecode original_text = "I'm drinking a café in a cafe." unidecoded_text = unidecode(original_text) regex = r'cafe' re.sub(regex, 'X', unidecoded_text)
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2 Comments

Thanks but this won't help as I'd like to keep other accents from the origian stirng.
@AntoineDusséaux Right, I didn't thought about that. The other answer seems to be correct.
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Instead of removing accents, I needed to preserve accents on the text, then I used the following code:

accents_dic = { 'A': '(A|Á|À|Â|Ã)', 'E': '(E|É|È)', 'I': '(I|Í|Ï)', 'O': '(O|Ó|Ô|Õ|Ö)', 'U': '(U|Ú|Ü)', 'C': '(C|Ç)' } def define_regex_name(name): for i, j in accents_dic.items(): name = re.sub(i,j,name) return re.compile(name, re.IGNORECASE)
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