python dictionary has a list or get an empty (but iterable) list

gistfile1.txt

>>> for x in a.get('a list'):
...   print x
...
1
2
3
4
5
6
>>> for x in a.get('b list'):
...   print x
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'NoneType' object is not iterable
>>> for x in (a.get('b list') or []):
...   print x