Until Python 3.10, you had to use alternatives like the third-party regex module for possessive quantifiers and atomic grouping. The re module supports these features from Python 3.11 version.

Greedy and non-greedy quantifiers will backtrack to help the overall pattern to succeed. The syntax for an atomic group is (?>pat), where pat is the pattern you want to safeguard from further backtracking. You can think of it as a special group that is isolated from the other parts of the regular expression.

Here's an example with greedy quantifier:

>>> import re
>>> numbers = '42 314 001 12 00984'

# 0* is greedy and the (?>) grouping prevents backtracking
# same as: re.findall(r'0*+\d{3,}', numbers)
>>> re.findall(r'(?>0*)\d{3,}', numbers)
['314', '00984']

Here's an example with non-greedy quantifier:

>>> ip = 'fig::mango::pineapple::guava::apples::orange'

# this matches from the first '::' to the first occurrence of '::apple'
>>> re.search(r'::.*?::apple', ip)[0]

# '(?>::.*?::)' will match only from '::' to the very next '::'
# '::mango::' fails because 'apple' isn't found afterwards
# similarly '::pineapple::' fails
# '::guava::' succeeds because it is followed by 'apple'
>>> re.search(r'(?>::.*?::)apple', ip)[0]

Video demo:

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