[Thom*]

Here I have documented the function in detail and I have included the debug (print) statements so you can see the results. I hope it helps.

'''Begin with what I assume is kovidgoyal's Python funtion "replace" that gives access to file_name and search data.'''
def replace(match, number, file_name, metadata, dictionaries, data, functions, *args, **kwargs):

    '''Simply key in the desired text to begin the replace string.'''
    str1 = '<p id="id_'
    print(str1)

    '''Call the file_name and extract the 10th (inclusive) to the 5th (exclusive) from the end.'''
    str2 = file_name [-10:-5:]
    print(str2)

    '''Call the match, add zeros to the front and extract the last 3 digits.'''
    str3 = ("000" + match.group(1)) [-3:]
    print(str3)

    '''Key in the desired text for the middle of the replace string.'''
    str4 = '" class="calibre1"><sup class="calibre2">'
    print(str4)

    '''Call the match (unmolested).'''
    str5 = match.group(1)
    print(str5)

    '''Key in the desired text for the end of the replace string.'''
    str6 = '</sup>'
    print(str6)

    '''Concatenate the string.'''
    newid = (str1 + str2 + str3 + str4 + str5 + str6)
    print(newid)

    '''Return the replace string.'''
    return newid