in python what would be matched by "(4{5,6})\1"?

Question

explain

Answer 1

Looks like a regular expression.

(4{5,6}) is a 4 that is repeated five or six times. The whole expression is a capturing group because of the parentheses

\1 is one repetition of the first capturing group.

So the expression would match 4444444444 or 444444444444 (=10 or 12 times '4')

Answer 2

Actually, I'd expect it to find matches in *all* strings which have at least 10 consecutive 4s.
In order for the capturing group to be repeated, there should be at least ten 4s present, but not necessarily *exactly* tens or twelves of those.
For example, if you have a string containing 16 or 23 4s -- it will also match.

Answer 3

I'd say that depends on the regex method that is used.

import re

ptrn = re.compile(r'(4{5,6})\1')

s = '807654354444444444123456djs'

print(ptrn.search(s))
# <_sre.SRE_Match object; span=(8, 18), match='4444444444'>

print(ptrn.match(s))
# None

s = '444444444444444444444444444444444'

print(ptrn.search(s))
# <_sre.SRE_Match object; span=(0, 12), match='444444444444'>

print(ptrn.match(s))
# <_sre.SRE_Match object; span=(0, 12), match='444444444444'>

for t in ptrn.finditer(s):
print('>>>', t)
# >>> <_sre.SRE_Match object; span=(0, 12), match='444444444444'>
# >>> <_sre.SRE_Match object; span=(12, 24), match='444444444444'>

Answer 4

Anna A-greedy ;)

Answer 5

10 or 12 fours