Python RegEx代码可检测句子中的特定功能

Question

I created a simple word feature detector. So far been able to find particular features (jumbled within) the string, but the algorithm get confused with certain sequences of words. Let me illustrate:

from nltk.tokenize import word_tokenize
negative_descriptors = ['no', 'unlikely', 'no evidence of']
negative_descriptors = '|'.join(negative_descriptors)
negative_trailers = ['not present', 'not evident']
negative_trailers = '|'.join(negative_descriptors)

keywords = ['disc prolapse', 'vertebral osteomyelitis', 'collection']

def feature_match(message, keywords, negative_descriptors):
    if re.search(r"("+negative_descriptors+")" + r".*?" + r"("+keywords+")", message): return True
    if re.search(r"("+keywords+")" + r".*?" + r"("+negative_trailers+")", message): return True

The above returns True for the following messages:

message = 'There is no evidence of a collection.' 
message = 'A collection is not present.'

That is correct as it implies that the keyword/condition I am looking for is NOT present. However, it returns None for the following messages:

message = 'There is no evidence of disc prolapse, collection or vertebral osteomyelitis.'
message = 'There is no evidence of disc prolapse/vertebral osteomyelitis/ collection.'

It seem to be matching 'or vertebral osteomyelitis' in the first message and '/ collection' in the second message as negative matches, but this is wrong and implies that the message reads 'the condition that I am looking for IS present'. It should really be returning 'True' instead.

How do I prevent this?

Answer 1

There are several problems with the code you posted :

1. negative_trailers = '|'.join(negative_descriptors) should be negative_trailers = '|'.join(negative_trailers )
2. You should also convert your list keywords to string as you did for your other lists so that it can be passed to a regex
3. There is no use to use 3 times 'r' in your regex

After these corrections your code should look like this :

negative_descriptors = ['no', 'unlikely', 'no evidence of']
negative_descriptors = '|'.join(negative_descriptors)
negative_trailers = ['not present', 'not evident']
negative_trailers = '|'.join(negative_trailers)

keywords = ['disc prolapse', 'vertebral osteomyelitis', 'collection']
keywords = '|'.join(keywords)

if re.search(r"("+negative_descriptors+").*("+keywords+")", message): neg_desc_present = True
if re.search(r"("+keywords+").*("+negative_trailers+")", message): neg_desc_present = True