Regex {} question

Question

Looking at this code https://code.sololearn.com/433/#py
I don't understand, why changing line 3 to r"9{0,3}

Answer 1

Nassim Abed don't you think an empty string will match 0 9's.

You can also check by doing the below.

import re

pattern = r"89{0,3}quot;

if re.match(pattern, "8"):
print("Match 1")

if re.match(pattern, "899"):
print("Match 2")

if re.match(pattern, "8999"):
print("Match 3")

Answer 2

Your regex is explicitly looking for the number 9. Any other character will not match. Zero 9 is not 8

Answer 3

How could you match 8 when the pattern is to just match 0 to 3 nines in the string.

Answer 4

Ok then what exactly will match zero 9's?

Answer 5

Use a range
[1-8]{1,3}
This will match any number between 1 and 8. You can change the range ( ex: change 1 to 0 to match numbers from 0 to 8) and the quantifiers to fit your needs.

Answer 6

Thanks for the workaround. Workarounds aside, what is the syntax for matching zero repetitions? I am struggling to understand how Python deals with the logic of it. It seems so far that null is not zero, which is clear enough, but still doesn't answer the question: how to modify this code, what will match zero 9's without changing r"9{0,3}quot;??

Answer 7

:) Thank you Avinesh.