Python正则表达式集合中有0个或更多单词

Question

I have a big block of text within which I am trying to look for a phrase. The phrase can be structured in a number of different ways.

1. First I want to look for a word from a set of words, let's call it set 1.
2. After that there must be a space or comma (or maybe something else that separates words)
3. Then there may be 0 or more words from set 2
4. Again followed by the word separation characters as in point 2 above
5. finally there should be a word from set 3

Ideally all of these should be in the same sentence.

set 1 = (Potential|Ability|Possibility|need|requires|needs|plenty|for|Needing|Requiring)

set 2 = (for|to|of|full|a|be|complete|Internal)

set 3 = (renovate|improve|modernise|modernize|update|renovating|improving|modernising|modernizing|updating|potential|project|renovation)

So I have this regex expression

(Potential|Ability|Possibility|need|requires|needs|plenty|for|Needing|Requiring)[ ,]*(for|to|of|full|a|be|complete|Internal)[ ,]*(renovate|improve|modernise|modernize|update|renovating|improving|modernising|modernizing|updating|potential|project|renovation)

Now this will match a phrase where there is 0 or 1 words from set 2 but not if there are multiples. eg "provides a wonderful opportunity for someone to add their own stamp as the property needs complete renovation throughout."

as soon as I add in 'a' before 'complete' it fails. The same as if I add another 'complete'.

How do I specify to look for 0 or multiple words from a set?

Answer 1

Set 1: Matches any of the words in set 1 with 1 separator.

(Potential|Ability|Possibility|need|requires|needs|plenty|for|Needing|Requiring)[ ,]

Set 2: Matches any of the words in set 2 with 1 separator, 0 or more times.

((for|to|of|full|a|be|complete|Internal)[ ,])*

Set 3: Matches any of the words in set 3

(renovate|improve|modernise|modernize|update|renovating|improving|modernising|modernizing|updating|potential|project|renovation)

Full:

(Potential|Ability|Possibility|need|requires|needs|plenty|for|Needing|Requiring)[ ,]((for|to|of|full|a|be|complete|Internal)[ ,])*(renovate|improve|modernise|modernize|update|renovating|improving|modernising|modernizing|updating|potential|project|renovation)

Answer 2

Long alternatives in regular expressions can be quite slow . I'd suggest to take another approach. First segment the text (split to words) and the iterate over the array of words checking if subsequent sets of 3 words fulfil your requirements

Something like that (rather pseudocode than a real python):

def check(text):
  words = segment(text)
  for i in range(0, len(text)-2):
      check_word1(text[i]) and check_word1(text[i+1]) and check_word3(text[i+2])

Answer 3

You have to use this regex:

(Potential|Ability|Possibility|need|requires|needs|plenty|for|Needing|Requiring)[ ,](for|to|of|full|a|be|complete|Internal)*[ ,](renovate|improve|modernise|modernize|update|renovating|improving|modernising|modernizing|updating|potential|project|renovation)

Because you have one word from first set. After that you have one space or comma. Near you have 0 or more word from set 2. Then an other space or comma and finally one word from the last set.

Answer 4

Just in case you didn't know, you can use sites like https://regex101.com/ to test your regular expressions, and see why it works/it doesn't.

In this case, you need the "zero or more" ( * ) operator on your second group. The result would be:

(Potential|Ability|Possibility|need|requires|needs|plenty|for|Needing|Requiring)[ ,]*(for|to|of|full|a|be|complete|Internal)*[ ,]*(renovate|improve|modernise|modernize|update|renovating|improving|modernising|modernizing|updating|potential|project|renovation)

However, considering you probably want the words to be separated, just include the space on the operator (you can use a non-capturing group for that), resulting on:

(Potential|Ability|Possibility|need|requires|needs|plenty|for|Needing|Requiring)[ ,]*(?:(for|to|of|full|a|be|complete|Internal)[ ,]*)*(renovate|improve|modernise|modernize|update|renovating|improving|modernising|modernizing|updating|potential|project|renovation)