Remove punctuation from Unicode formatted strings

Question

I have a function that removes punctuation from a list of strings:

def strip_punctuation(input):
    x = 0
    for word in input:
        input[x] = re.sub(r'[^A-Za-z0-9 ]', "", input[x])
        x += 1
    return input

I recently modified my script to use Unicode strings so I could handle other non-Western characters. This function breaks when it encounters these special characters and just returns empty Unicode strings. How can I reliably remove punctuation from Unicode formatted strings?

Answer 1

You could use unicode.translate() method:

import unicodedata
import sys

tbl = dict.fromkeys(i for i in xrange(sys.maxunicode)
                      if unicodedata.category(unichr(i)).startswith('P'))
def remove_punctuation(text):
    return text.translate(tbl)

You could also use r'\\p{P}' that is supported by regex module :

import regex as re

def remove_punctuation(text):
    return re.sub(ur"\p{P}+", "", text)

Answer 2

If you want to use JF Sebastian's solution in Python 3:

import unicodedata
import sys

tbl = dict.fromkeys(i for i in range(sys.maxunicode)
                      if unicodedata.category(chr(i)).startswith('P'))
def remove_punctuation(text):
    return text.translate(tbl)

Answer 3

You can iterate through the string using the unicodedata module's category function to determine if the character is punctuation.

For possible outputs of category , see unicode.org's doc on General Category Values

import unicodedata.category as cat
def strip_punctuation(word):
    return "".join(char for char in word if cat(char).startswith('P'))
filtered = [strip_punctuation(word) for word in input]

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Additionally, make sure that you're handling encodings and types correctly. This presentation is a good place to start: http://bit.ly/unipain

Answer 4

A little shorter version based on Daenyth answer

import unicodedata

def strip_punctuation(text):
    """
    >>> strip_punctuation(u'something')
    u'something'

    >>> strip_punctuation(u'something.,:else really')
    u'somethingelse really'
    """
    punctutation_cats = set(['Pc', 'Pd', 'Ps', 'Pe', 'Pi', 'Pf', 'Po'])
    return ''.join(x for x in text
                   if unicodedata.category(x) not in punctutation_cats)

input_data = [u'somehting', u'something, else', u'nothing.']
without_punctuation = map(strip_punctuation, input_data)