Questions about using Regex Search & Replace in gedit

I am trying to use the Regex Search & Replace plugin of gedit.

1. I want to search for a digit that repeats 2 or 3 times, so I thought the regex was

   [0-9]\{2,3\}
   

   But it doesn't match the targets it should, such as "22".

2. I want to find a word "Notes" exactly, so I thought it would be

   \<Notes\> 
   

   But it doesn't work either.

3. How to add a "#" in front of a string of any three digits "[0-9][0-9][0-9]"? e.g. "123" becomes "#123".

I was wondering if I made some mistake? I am using Basic Regex. What type of Regex is used in the plugin? How can I learn how to use this plugin?

You should not need to escape your regex characters. Your first example should be:

[0-9]{2,3}

Your second example should be:

\bNote\b

For the third situation, you'll need to match things before and after, then use back-references:

(.*)([0-9]{3}.*)

with the replacement being:

\1p\2

For more details, see pydoc re that will tell you about Python regular expression syntax, or the online documentation.

As Kees says, the plugin uses Python's re module syntax, which also has a How-To on the python site.

I also recommend installing and playing around with kodos .
It's a python regular expression tester (it calls itself a 'debugger'), and includes a quick reference regex sheet as well as a shorter version of the re module documentation.

The regular-expression.info site has a nice comparison of different implementations of regular expression meta-languages. There's a decent section on the python flavor there as well.