Cannot extract all words using word or whitespace boundary with regex

Question

I need extract double Male-Cat:

a = "Male-Cat Male-Cat Male-Cat-Female"
b = re.findall(r'(?:s|^)Male-Cat(?:s|$)', a)
print (b)
['Male-Cat ']

c = re.findall(r'bMale-Catb', a)
print (c)
['Male-Cat', 'Male-Cat', 'Male-Cat']

I need extract tree times Male-Cat:

a = "Male-Cat Male-Cat Male-Cat"
b = re.findall(r'(?:s|^)Male-Cat(?:s|$)', a)
print (b)
['Male-Cat ', ' Male-Cat']

c = re.findall(r'bMale-Catb', a)
print (c)
['Male-Cat', 'Male-Cat', 'Male-Cat']

Another strings which are parsed correctly by first way:

a = 'Male-Cat Female-Cat Male-Cat-Female Male-Cat'
a = 'Male-Cat-Female'
a = 'Male-Cat'

Something missing? Can you explain what is wrong and what is correct way?

Asked By: jezrael

||

Source

Answer 1

Use lookarounds to extract words inside whitespace boundaries:

r'(?<!S)Male-Cat(?!S)'

See the online regex demo

Details

(?<!S) – a whitespace or start of string must appear immediately to the left of the current location
Male-Cat – the term to search for
(?!S) – a whitespace or end of string must appear immediately to the right of the current location

Since (?<!S) and (?!S) are zero-width assertions, the whitespace won’t be consumed, and consecutive matches will get found.

Answered By: Wiktor Stribiżew

Cannot extract all words using word or whitespace boundary with regex

Question:

Answers: