How can regex find the middle three letters of a 5char-word?

Question

Example findall(regex,"12345")=234
General case: find string w.o first and last.

Answer 1

Oma Falk Based on the question:

"How can regex find the middle 3 letters of a 5 char-word?"

I'm assuming the word can include any non-whitespace alphanumeric character like this one: "12345"

The regexes in this thread would work with this example.

However, many may also incorrectly work for the following invalid values:

" 234 "
" 2345"
"1234 "
"1 3 5"
"123 5"

The same regexes may not properly extract "234" from 5 char values with leading and/or trailing whitespaces like the following:

" 12345"
"12345 "
" 12345 "

I believe the proper regex to cover all positive and negative test cases would be:

re.search(r'(?<!\S)\S(\S{3})\S(?!\S)', s)

- The \S matches on non whitespace characters.
- (?<!\S) is a negative look behind.
- (?!\S) is a negative look ahead.

To match on all but the first and last characters, replace (\S{3}) with (\S+)

The code below runs tests on the RegEx patterns posted in this thread for review with mine posted last:

https://code.sololearn.com/cnnrMYDDmP2x/

I hope this helps.

Answer 2

import re
print(re.findall(r".(.{3}).", "12345"))

print(re.findall(r".(.{3}).", "hello"))

print(re.findall(r".(.{3}).", "12AA5"))
same "pattern" used for all three.

Answer 3

reg = re.compile(r'^(\d|\w)(\d{3}|\w{3})(\d|\w)#x27;)

mo = reg.search('12345')

print(mo.group(2))

It works for letters or numbers. Not both

Answer 4

Slick got it!

https://code.sololearn.com/czuv7g9yUI1A/?ref=app

Answer 5

Code Crasher want to learn regex.
It is very mighty.

After 3 hours I could find a regex for a String if it is a tictactoe winner.
Hope to become a bit quicker.

Answer 6

Ahhh groups...good.

Answer 7

Code Crasher
Yes...wehre else👍👍

Answer 8

reg = r"\B.+\B"

"The \B metacharacter is used to find a match, but where it is NOT at the beginning/end of a word." w3Schools.com

Answer 9

Regex is such a lovely topic.
You could use a lookaround pattern (lookbehind and lookahead), like:

import re
m=re.match(r"(?<=.).{3}(?=.)", your_5_chr_str).group()

(since + and other special characters are greedy, you don't have to specify {3} though.)

You could also capture it in a group:
m=re.match(r".(.+).",your_5_chr_str).group(1)

Answer 10

This is what helped me get to grips with regular expression after the tutorial in Sololearn:-
https://www.w3schools.com/JUMP_LINK__&&__python__&&__JUMP_LINK/python_regex.asp

Answer 11

David Carroll yeeeees got it for 90%

Answer 12

Code Crasher brilliant

Answer 13

Folks... I need a regex for my feed post with state machine.