recursion - Walk recursively through childs of a list in Python -

i try recursively print sentences nested list of lists

i want obtain list containing

['big bad dog', 'big fluffy cat', 'small blue happy pony', 'small frog']

here code, don't work...

am on right path or should structure data in way achieve goal?

from pprint import pprint  dirs = [  {      'kw': 'big',     'childs': [         {              'kw': 'bad',             'childs': [                 {                     'kw': 'dog'                 }             ]         },         {             'kw': 'fluffy',             'childs': [                 {                     'kw': 'cat'                 }             ]         }      ] },  {      'kw': 'small',     'childs': [         {              'kw': 'blue',             'childs': [                 {                      'kw': 'happy',                     'childs': [                         {                              'kw': 'pony'                          }                      ]                 }             ]         },         {             'kw': 'frog'          }      ] }, ]   def traverse(d, l):      kw = d.get('kw')     c = d.get('childs')     l.append(kw)     if c:         cc in c:            l = traverse(cc, l)    return l   r = traverse(dirs[0], [])  pprint(r) 

as usual, generators work nicely recursive structures

def traverse(i):     d in i:         childs = d.get('childs')         j in traverse(childs) if childs else ['']:             yield d['kw']+' '+j  res = list(traverse(dirs)) 

in python3.3, becomes

def traverse(i):     d in i:         c = d.get('childs')         yield (d['kw']+' '+j j in (traverse(c) if c else ['']))