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Fix #1924893 [English text in code block (manual)](https://bugs.launchpad.net/calibre/+bug/1924893)

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Kovid Goyal 2021-04-18 13:38:18 +05:30
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manual/regexp.rst
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@ -60,14 +60,20 @@ You can of course do that: Just put a backslash in front of any special characte
So, what are the most useful sets?
------------------------------------
Knew you'd ask. Some useful sets are ``[0-9]`` matching a single number, ``[a-z]`` matching a single lowercase letter, ``[A-Z]`` matching a single uppercase letter, ``[a-zA-Z]`` matching a single letter and ``[a-zA-Z0-9]`` matching a single letter or number. You can also use an escape sequence as shorthand::
Knew you'd ask. Some useful sets are ``[0-9]`` matching a single number, ``[a-z]`` matching a single lowercase letter, ``[A-Z]`` matching a single uppercase letter, ``[a-zA-Z]`` matching a single letter and ``[a-zA-Z0-9]`` matching a single letter or number. You can also use an escape sequence as shorthand:
\d is equivalent to [0-9]
\w is equivalent to [a-zA-Z0-9_]
\s is equivalent to any whitespace
``\d``
is equivalent to ``[0-9]``
``\w``
is equivalent to ``[a-zA-Z0-9_]``
``\s``
is equivalent to any whitespace
.. note::
"Whitespace" is a term for anything that won't be printed. These characters include space, tabulator, line feed, form feed and carriage return.
"Whitespace" is a term for anything that won't be printed. These characters include space, tabulator, line feed, form feed, carriage return, non-breaking spaces, etc.
As a last note on sets, you can also define a set as any character *but* those in the set. You do that by including the character ``"^"`` as the *very first character in the set*. Thus, ``[^a]`` would match any character excluding "a". That's called complementing the set. Those escape sequence shorthands we saw earlier can also be complemented: ``"\D"`` means any non-number character, thus being equivalent to ``[^0-9]``. The other shorthands can be complemented by, you guessed it, using the respective uppercase letter instead of the lowercase one. So, going back to the example ``<p[^>]*>`` from the previous section, now you can see that the character set it's using tries to match any character except for a closing angle bracket.