pythonregexstringfindallboundary

Cannot extract all words using word or whitespace boundary with regex


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-Cat\b', 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-Cat\b', 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?


Solution

  • Use lookarounds to extract words inside whitespace boundaries:

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

    See the online regex demo

    Details

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