I want to change the third comma in this string using regex in notepad

145, 45, 67, 688

With a ":" Like this :

145, 45, 67: 688

I tried this

(?:,)(,)*

I think I am missing something

CodePudding user response：

You can use this regular expression in the dialog window:

Find what: ^(([^,]*,){2}[^,]*),

Replace with: \1:

The first ^ matches at the start of the line. The expression ([^,]*,){2} matches everything up to a comma two times. The expression [^,]* then matches everything up to, but excluding, the third comma. The first so called capture group is referred to by \1. In this case it refers to what's inside the outermost parentheses.

CodePudding user response：

If the third comma is always the last, you can check for the end of the string/line with $:

,(?=[^,]*$)

Demo: