正则表达式两个可选组，而不仅仅是第一组

Question

I want a regex that will capture words with two optional prefixes, but not the first one alone. I'm using Python 3.6. It should capture

cat
nicecat
bigcat

and any prefixes before those two, like

supernicecat
fatbigcat

but it should NOT capture

fatcat
supercat
xyzcat

Here's what I have so far. It's not quite working.

\b(\w+)?(?:big|nice)?cat\b

Answer 1

Wrap them in another group:

\b(?:(\w+)?(?:big|nice))?cat\b

Live demo

Answer 2

You can do something like this

\b(?:\w*?(?:big|nice))?cat\b

Put the \\w* into the optional group.

Answer 3

Here you go:

^(?:[a-z]*(?:big|nice))?cat$

Be sure to enable multi-line flag. I am assuming each entry is on its own line.

The problem with your Regex is that you made big|nice or nothing due to the question mark. What I am proposing is to add [az]* before it then add a question mark over (?:[az]*(?:big|nice)) expression in order to allow standalone cat to match.