Help - Learning to use Regex Functions

[weberr]

Struggling to understand use of Regex Functions capability -- primarily how to introduce function arguments. Maybe if someone can illustrate with an example, I can take it from there.

For instance:
If I have a set of lines in an epub document such as:
<p>chapter 1</p>
<p>chapter 1</p>
<p>chapter 1</p>
<p>chapter 1</p>

and what I want is:
<p>chapter 1</p>
<p>chapter 2</p>
<p>chapter 3</p>
<p>chapter 4</p>

Using the Increment() Function, what would the Find and Function lines look like?

Thanx for your help.

[jbacelar]

Search (selected files):
(<p>chapter )\d+

Regex-Function:

def replace(match, number, file_name, metadata, dictionaries, data, functions, *args, **kwargs):
    num=number
    return match.group(1)+str(num)
replace.file_order = 'spine'

And:
Replace all.

Useful link:
http://manual.calibre-ebook.com/function_mode.html