[Regex] Matching doubts

Question

Can someone explain why the first example match and how could I match any number from 1 to 31, in the code you can see what I tried, dont know why it only matches one digit though.
https://code.sololearn.com/cymM0q4aMw5C/?ref=app

Answer 1

Abhay 😆
A misunderstanding. 😲
I am saying that in the FIRST expression there are 2 "-" if you see carefully, the first "-" between a and z is fine but the second "-" was creating problems! So, using a "\" will work perfectly!

Rodrigo Tallar That is because the regex found "_asd" in its match! It broke as soon as a "." came in the way!

Answer 2

0?[1-9]|[1-2]\d|30|31

In the second match for string 31
It is checking if it starts with 0 or not and then finds 3 from the expression [1-9] so you get your first and only match and it doesn't needs to check other "or" conditions

Answer 3

Rodrigo Tallar
In the first case:
I have given the reason for the match!
But in case if the string starts from a dog '.' then just remove that '-' sign from the variable local, and see the result! The '-' is also used in 'a-z' or 'A-Z' and all. So the system got confused!

And for the second match Abhay has given the answer 😃

Answer 4

Namit Jain thks a lot! didn't noticed that if a-z has a special meaning and stands for all characters between a and z ,so was with +-/ which was checking for characters between + and / and escaping it diminished that special meaning

Answer 5

Just add a '+' sign in line 4
And you will get the expected results!

The first regex will check only if the first letter is there in the 'local' variable or not 🙂

Answer 6

Adding '+' to the fourth line makes numbers like 292 match, which clearly are not between 1-31, already fixed it placing a '#x27; at the end. Not sure what you mean with the second regex, but starting the string with a '.' still makes it match

Answer 7

No Abhay
The reason for matching of strings beginning with dots in the first case is due to the presence of "-". (read my answer)

Answer 8

Abhay I am talking about the second "-"
The first one is perfectly alright!

Answer 9

Rodrigo Tallar
FYI, https://stackoverflow.com/questions/766372/JUMP_LINK__&&__python__&&__JUMP_LINK-non-greedy-regexes

https://code.sololearn.com/cL4AGuMdMb9d/?ref=app

Answer 10

Already fix that part with '#x27; at the end.
0? Is because I want numbers like 01-09 to be accepted as well as 1-9

For the second regex I should have escaped - right?

Answer 11

In the first one
Even if you use this it will match whole expression and the main character that I haven't been able to understand yet from the following is "!" ,if you remove it won't match dots ,but keeping it matches dots

r"[a-z!-_]+"

Answer 12

yea that's what I said it checks starting with 0 or not ,even if 0 doesn't exist match will continue checking for other part of expression

Answer 13

Namit Jain how so? a-z accepts a b c d e f not "." (dots)

Answer 14

Namit Jain lol ! I am talking about first one and that's the only concern for me , first one matches whole string when it shouldn't for dots ,but it does possibly because of exclamation mark
Second one I already explained ,

Maybe someone else can explain better than me and possibly answer my question as well

Answer 15

Updated the code and escaped '-' Now it doesn't match dots, but it still matches the string before them. Any ideas?