Regex - How to remove a word, capitalize next

[MerlinMama]

Is there a way to replace "But they wanted..." with "They wanted..." in one search and replace operation, or do I need to continue with my current two-step process? (Remove 'But' in first, capitalize 'they' in the second)

[DNSB]

You could search for 'But ([a-z])' and replace with '\u\1' which will replace any But followed by a lower case letter with the upper case letter.

[MerlinMama]

I get the following error when I try to run it

calibre, version 6.26.0
ERROR: Unhandled exception: <b>error</b>:incomplete escape \u at position 3

calibre 6.26  embedded-python: True
Windows-10-10.0.22621-SP0 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.22621')
Python 3.10.1
Windows: ('10', '10.0.22621', 'SP0', 'Multiprocessor Free')
Interface language: None
Successfully initialized third party plugins: Count Pages (1, 13, 2) && Diaps Editing Toolbag (0, 4, 0) && FanFicFare (4, 27, 0) && Favourites Menu (1, 3, 0) && Find Duplicates (1, 10, 8) && Generate Cover (2, 3, 3) && Job Spy (1, 0, 239) && Kobo Utilities (2, 16, 10) && Save To Format (0, 0, 6) && View Manager (1, 10, 2)
Traceback (most recent call last):
  File "calibre\gui2\tweak_book\boss.py", line 1129, in search
  File "calibre\gui2\tweak_book\search.py", line 1562, in run_search
  File "calibre\gui2\tweak_book\search.py", line 1469, in do_replace
  File "calibre\gui2\tweak_book\editor\widget.py", line 328, in replace
  File "calibre\gui2\tweak_book\editor\text.py", line 599, in replace
  File "regex\regex.py", line 700, in _compile_replacement_helper
  File "regex\_regex_core.py", line 1690, in _compile_replacement
  File "regex\_regex_core.py", line 1757, in parse_repl_hex_escape
regex._regex_core.error: incomplete escape \u at position 3

[DNSB]

Sorry about that. I'm more used to the dialect of Regex used by Sigil which does accept \u to convert to one character to upper case.

According to a post by Kovid Goyal, calibre does not support \u and you will need to use function mode: https://manual.calibre-ebook.com/function_mode.html which is considerably more complex.

Yet another reason that I use both calibre's ebook-editor and Sigil. They both offer capability that the other does not.

[lomkiri]

Easy enough:
Search : But ([a-z])
regex-function :

def replace(match, number, file_name, metadata, dictionaries, data, functions, *args, **kwargs):
    return match[1].upper()

[MerlinMama]

Thank you, that worked! I really appreciate it.