Regex phone number question python course

Question

I'm trying to understand why my code doesn't work. In the problem, it says the phone number should start with 1,8 or 9 and it should have exactly 8 digits. I couldn't understand why my code accepts less than 8 digits or more than 8 digits. https://code.sololearn.com/c2A14380a14a/#py

Answer 1

your pattern doesn't works as you expect:

pattern = r"^1|8|9\d{7}quot;

check if string start with 1 (and anything else after), contains 8 (and implicitly start by using 'match'), or ends (and implicitly start with 'match') with 9 followed by 7 digits...

correct one (by using 'match') could be:

pattern = r"(1|8|9)\d{7}quot;

or:

pattern = r"[189]\d{7}quot;

Answer 2

Baran Aldemir , "|" metacharacter means "either or". When your string starts with 1, 8 or 9 it's true that's why it doesn't check after that.

Answer 3

Baran Aldemir I have explained in details how your pattern work in my first post/answer here ^^

Answer 4

Baran Aldemir , change the pattern => pattern = r"^[189]\d{7}quot;

Answer 5

@visph @TheWhiteCat Actually I know those are the answers but I was trying to understand why without parentheses it doesn't work. In other words, what does python interpret from my code?