prefix matching in python

Question

I have a string like:

" This is such an nice artwork"

and I have a tag_list ["art","paint"]

Basically, I want to write a function which accepts this string and taglist as inputs and returns me the word "artwork" as artwork contains the word art which is in taglist.

How do i do this most efficiently?

I want this to be efficient in terms of speed

 def prefix_match(string, taglist):
        # do something here
     return word_in string

Answer 1

Try the following:

def prefix_match(sentence, taglist):
    taglist = tuple(taglist)
    for word in sentence.split():
        if word.startswith(taglist):
            return word

This works because str.startswith() can accept a tuple of prefixes as an argument.

Note that I renamed string to sentence so there isn't any ambiguity with the string module.

Answer 2

Try this:

def prefix_match(s, taglist):
    words = s.split()
    return [w for t in taglist for w in words if w.startswith(t)]

s = "This is such an nice artwork"
taglist = ["art", "paint"]
prefix_match(s, taglist)

The above will return a list with all the words in the string that match a prefix in the list of tags.

Answer 3

Here is a possible solution. I am using regex, because I can get rid of punctuation symbols easily this way. Also, I am using collections.Counter this might add efficiency if your string has a lot of repeated words.

tag_list =  ["art","paint"]

s = "This is such an nice artwork, very nice artwork. This is the best painting I've ever seen"

from collections import Counter
import re

words = re.findall(r'(\w+)', s)

dicto = Counter(words)

def found(s, tag):
    return s.startswith(tag)

words_found = []

for tag in tag_list:
    for k,v in dicto.iteritems():
        if found(k, tag):
            words_found.append((k,v))

The last part can be done with list comprehension:

words_found = [[(k,v) for k,v in dicto.iteritems() if found(k,tag)] for tag in tag_list]

Result:

>>> words_found
[('artwork', 2), ('painting', 1)]