sre negated lookaheads/behinds

[Robin Becker]

I think the documentation is unclear/wrong about how look behinds etc
work.

wpat = re.compile(r'(?<!self\.)\b([A-Za-z_]\w*)\s*\(')

fails for 

wpat.search('   a(')

and succeeds for 

wpat.search('      a(')


I guess because internally the matcher is using the negated positive
look behind.

Clearly my a( is not preceded by self. in either case. However, in the
first case as there is not enough room for the positive look behind I
think it is wrongly failing to match. Is this correct?

I know the documentation mentions that the (?< ... ) patterns must be
fixed length, but nowhere does it say that negated patterns must be
fixed length.
-- 
Robin Becker