REGEX Look Arounds

[CharlesKL]

Hi, I am trying to learn and understand look arounds, In the code below why is '1' removed and not !123!

a = "learn@123Python456"
re.findall(r"\d+", a)   #['123', '456']
re.findall(r"(?<!\W)\d+", a)   #['23', '456']

while if I use a positive look behind such as:

b = "@@@coding????isfun"
re.findall(r"\w+", b)   #['coding', 'isfun']
re.findall(r"(?<=\W)\w+", b)   #['coding', 'isfun']

All the characters are retained

I was using IDLE to run the code

---

Actually this is a better example of a positive look behind

b = "@@@coding  isfun"
re.findall(r"\w+", b) #['coding', 'isfun']
re.findall(r"(?<=\s)\w+", b) #['isfun']

any assistance will be appreciated, thanks