I'm trying to create a regex to find the last dot in a string not preceded by a slash.

r = MyLine.Text.Swap\ Numbered\ and\ Unnumbered\ List.From\ -\ -\ -\ to\ Numbered\ list\ 1\.\ 2\.\ 3\.\ 

What I want to find as match is "From\ -\ -\ -\ to\ Numbered\ list\ 1\.\ 2\.\ 3\.\"

I tried to reverse the string but that didn't work either re.findall(".*\\.(?!\\\)", r[::-1])

What did I wrong?

I'm trying to create a regex to find the last dot in a string not preceded by a slash.

r = MyLine.Text.Swap\ Numbered\ and\ Unnumbered\ List.From\ -\ -\ -\ to\ Numbered\ list\ 1\.\ 2\.\ 3\.\ 

What I want to find as match is "From\ -\ -\ -\ to\ Numbered\ list\ 1\.\ 2\.\ 3\.\"

I tried to reverse the string but that didn't work either re.findall(".*\\.(?!\\\)", r[::-1])

What did I wrong?

• python
• python-3.x
• regex

• Are you SURE the string actually contains backslashes? It is easy to be fooled by string escapes. And as it is, there are NO dots in that string not preceded by a backslash. – Tim Roberts Commented Nov 16, 2024 at 18:53
• Please provide the code you use to define the example string, run the regex and display the result. Note that the assignment to r is not valid Python. – trincot Commented Nov 16, 2024 at 19:16

1 Answer 1

You might use a negative lookbehind matching a dot, and then assert that what is to the left is not a \ followed by a dot.

Then you could capture what comes after it in group 1 which would be returned by re.findall

.*\.(?<!\\\.)(.*)

See a regex demo and a Python demo

For example:

import re

pattern = r".*\.(?<!\\\.)(.*)"

r = "MyLine.Text.Swap\\ Numbered\\ and\\ Unnumbered\\ List.From\\ -\\ -\\ -\\ to\\ Numbered\\ list\\ 1\\.\\ 2\\.\\ 3\\.\\ "

matches = re.findall(pattern, r)
print(matches)

Output

['From\\ -\\ -\\ -\\ to\\ Numbered\\ list\\ 1\\.\\ 2\\.\\ 3\\.\\ ']