适用于Python的嵌套正则表达式

Question

Is there a way to do nested regular expression in Python? For example I have

r1 = re.compile(r'SO ON')

can I have something like

r2 = re.compile(r'WHATEVER AND (r1)*') 

to validate "WHATEVER AND SO ON" for this example.

I tried finding about this around but couldn't find any solution.

Answer 1

r1 = re.compile(r'SO ON')
r2 = re.compile(r'WHATEVER AND (%s)*' % r1.pattern)

This isn't actually using any special feature of regex, it's using string formatting . Multiple strings can be passed in as:

r'WHATEVER AND (%s) (%s)' % (r1.pattern, 'hello')

Answer 2

I feel a moral obligation to point out that this is strictly supportive of regexen with no flags. As soon as you start using flags like re.MULTILINE this approach does not work. Perl was great with regex inside regex. I wish I could find a good Python solution.