CODEWITHSUNDEEP
pythonregex
kolonel
kolonel

Reputation: 1422

Formatting regular expressions in Python

I have a list of words 

wordlist = ['hypothesis' , 'test' , 'results' , 'total']

I have a sentence 

sentence = "These tests will benefit in the long run."

I want to check to see if the words in wordlist are in the sentence. I know that you could check to see if they are substrings in the sentence using:

for word in wordlist:
    if word in sentence:
        print word

However, using substrings, I start to match words that are not in wordlist, for example here test will appear as a substring in sentence even though it is tests that is in the sentence. I could solve my problem by using regular expressions, however, is it possible to implement regular expressions in a way to be formatted with each new word, meaning if I want to see if the word is in the sentence then:

for some_word_goes_in_here in wordlist:
    if re.search('.*(some_word_goes_in_here).*', sentence):
         print some_word_goes_in_here

so in this case the regular expression would interpret some_word_goes_in_here as the pattern that needs to be searched for and not the value of some_word_goes_in_here. Is there a way to format the input of some_word_goes_in_here so that the regular expression searches for the value of some_word_goes_in_here?

Upvotes: 1

Views: 355

Answers (3)

Martijn Pieters
Martijn Pieters

Reputation: 1121484

Use \b word boundaries to test for the words:

for word in wordlist:
    if re.search(r'\b{}\b'.format(re.escape(word)), sentence):
        print '{} matched'.format(word)

but you could also just split the sentence into separate words. Using a set for the word list would make the test more efficient:

words = set(wordlist)
if words.intersection(sentence.split()):
    # no looping over `words` required.

Demo:

>>> import re
>>> wordlist = ['hypothesis' , 'test' , 'results' , 'total']
>>> sentence = "These tests will benefit in the long run."
>>> for word in wordlist:
...     if re.search(r'\b{}\b'.format(re.escape(word)), sentence):
...         print '{} matched'.format(word)
... 
>>> words = set(wordlist)
>>> words.intersection(sentence.split())
set([])
>>> sentence = 'Lets test this hypothesis that the results total the outcome'
>>> for word in wordlist:
...     if re.search(r'\b{}\b'.format(re.escape(word)), sentence):
...         print '{} matched'.format(word)
... 
hypothesis matched
test matched
results matched
total matched
>>> words.intersection(sentence.split())
set(['test', 'total', 'hypothesis', 'results'])

Upvotes: 2

Jerry
Jerry

Reputation: 71538

Try using:

if re.search(r'\b' + word + r'\b', sentence):

\b are word boundaries which will match between your word and a non word character (a word character is any letter, digit or underscore).

For instance,

>>> import re
>>> wordlist = ['hypothesis' , 'test' , 'results' , 'total']
>>> sentence = "The total results for the test confirm the hypothesis"
>>> for word in wordlist:
...     if re.search(r'\b' + word + r'\b', sentence):
...             print word
...
hypothesis
test
results
total

With your string:

>>> sentence = "These tests will benefit in the long run."
>>> for word in wordlist:
...     if re.search(r'\b' + word + r'\b', sentence):
...          print word
...
>>>

Nothing is printed

Upvotes: 1

Alfe
Alfe

Reputation: 59426

I'd use this:

words = "hypothesis test results total".split()
# ^^^ but you can use your literal list if you prefer that
for word in words:
  if re.search(r'\b%s\b' % (word,), sentence):
    print word

You can even speed this up by using a single regexp:

for foundWord in re.findall(r'\b' + r'\b|\b'.join(words) + r'\b', sentence):
  print foundWord

Upvotes: 1

Related Questions