How to search for alphanumeric substring of specific length in Python?

Question

Say I have a string "ldhjshjds HdAjhdshj4 Hdsshj4 kdskjdshjdsjds"

I only want to search for substrings (alphanumeric only) starting with "H", but only if the string is between 10-20 characters.

"HdAjhdshj4" would be a match. "Hdsshj4" would not.

Would such a regex be costly on CPU cycles?

Answer 1

r"\\bH[A-Za-z0-9]{9,19}\\b"正是在寻找。

Answer 2

Use negative lookarounds.

re.findall(r'(?<!\S)H[A-Za-z0-9]{9,19}(?!\S)', s)

DEMO

Answer 3

您可以使用lookarounds来做到这一点。

re.findall(r'(?:^|(?<=\s))H[A-Za-z0-9]{9,19}(?=\s|$)', s)