How do I match exact strings from a list to a larger string taking white spaces into account?

Question

I have a large list of strings and I want to check whether a string occurs in a larger string. The list contains of strings of one word and also strings of multiple words. To do so I have written the following code:

example_list = ['pain', 'chestpain', 'headache', 'sickness', 'morning sickness']
example_text = "The patient has kneepain as wel as a headache"

emptylist = []
for i in example_text:
    res = [ele for ele in example_list if(ele in i)]
    emptylist.append(res)

However the problem is here is 'pain' is also added to emptylist which it should not as I only want something from the example_list to be added if exactly matches the text. I also tried using sets:

word_set = set(example_list)
phrase_set = set(example_text.split())
word_set.intersection(phrase_set)

This however chops op 'morning sickness' into 'morning' and 'sickness'. Does anyone know what is the correct way to tackle this problem?

Answer 1

Using PyParsing:

import pyparsing as pp

example_list = ['pain', 'chestpain', 'headache', 'sickness', 'morning sickness']
example_text = "The patient has kneepain as wel as a headache morning sickness"

list_of_matches = []

for word in example_list:
  rule = pp.OneOrMore(pp.Keyword(word))
  for t, s, e in rule.scanString(example_text):
    if t:
      list_of_matches.append(t[0])

print(list_of_matches)

Which yields:

['headache', 'sickness', 'morning sickness']

Answer 2

Nice examples have already been provided in this post by members.

I made the matching_text a little more challenging where the pain occurred more than once. I also aimed for a little more information about where the match location starts. I ended up with the following code.

I worked on the following sentence.

"The patient has not only kneepain but headache and arm pain, stomach pain and sickness"

import re
from collections import defaultdict

example_list = ['pain', 'chestpain', 'headache', 'sickness', 'morning sickness']
example_text = "The patient has not only kneepain but headache and arm pain, stomach pain and sickness"

TruthFalseDict = defaultdict(list)
for i in example_list:
    MatchedTruths = re.finditer(r'\b%s\b'%i, example_text)
    if MatchedTruths:
        for j in MatchedTruths:
            TruthFalseDict[i].append(j.start())

print(dict(TruthFalseDict))

The above gives me the following output.

{'pain': [55, 69], 'headache': [38], 'sickness': [78]}

Answer 3

You should be able to use a regex using word boundaries

>>> import re
>>> [word for word in example_list if re.search(r'\b{}\b'.format(word), example_text)]
['headache']

This will not match 'pain' in 'kneepain' since that does not begin with a word boundary. But it would properly match substrings that contained whitespace.