Question

I have clauses like a(b,c(d,e(f,g),h(i)))
and a string which has a number of clauses separated by a comma
for example, a(b,c(d,e(f,g),h(i))),a(b,c(d,e(f,g),h(i)))

Is there a way to extract variable and function names in their hierarchical order?
Suppose I want to print them as follows,

a
 b
 c
  d
  e
   f
   g
  h
   i 

how can I do this by using Python’s parser easily?
what regex should I use?

Answer 1

Regexes aren’t good for nested structures. But the string manipulation doesn’t have to be a big deal:

s = "a(b,c(d,e(f,g),h(i)))"

import re

level = 0
for tok in re.finditer(r"\w+|[()]", s):
    tok = tok.group()
    if tok == "(":
        level += 1
    elif tok == ")":
        level -= 1
    else:
        print "%s%s" % (" "*level, tok)

prints:

a
 b
 c
  d
  e
   f
   g
  h
   i