Stepping through regex pattern matches in Python: -

in python:

1. assignment not allowed in conditionals.
2. the state of regex match determined based on returned match object contains other match info.

now want match particular pattern out of 10 or 15, end cluttered this:

m = pat1.match(buffer) if m:         tok = tok1     val = m.group(0) else:     m = pat2.match(buffer)     if m:         tok = tok2          val = m.group(0)     else:         m = pat3.match(buffer)         if m:             tok = tok3             val = m.group(0)             # processing here , there - makes looping unsuitable         else:             m = pat4.match(buffer)             if m:                 tok = tok4                 val = m.group(0)             else:                     # ... keep indenting  

we have follows:

if match ... pat1:     tok =      val =  elif match ... pat2:     tok =      val =  elif match ... pat3:     tok =      val =  ... 

(like can done in other languages possibly using features like: assignment in conditionals, side effect standard match object, different form of match function pass reference args ...)

we can maybe use loop run through patterns, wouldn't suitable if there variations in processing each match.

so: there nice pythonic way keep match conditionals @ same level?!

loop on token , patterns in pairs, can adjust following:

for pat, token in zip([pat1, pat2, pat3], ['tok1', 'tok2', 'tok3']):     m = pat.match(buffer)     if m:         val = m.group(0)         tok = token1         break 

the idea build table before hand of pattern -> values:

tests = [     (re.compile('([a-z]{2})'), 'func1'),     (re.compile('(a{5}'), 'token2') ]  pattern, token in tests:     m = pattern.match(buffer)     if m:          # whatever 

this further extended provide callable instead take compiled object , buffer arguments , whatever wants , returns value.

eg:

def func1(match, buf):     print 'entered function'     return int(buf) * 50  tests = [      (re.compile('\d+'), func1) ]  pattern, func in tests:     m = pattern.match(buffer)     if m:         result = func(m, buffer)