def flatten(x):
r"""
>>> flatten("hello")
'hello'
>>> flatten({"a":[["hi"]]})
{'a': [['hi']]}
>>> flatten(None) is None
True
>>> flatten(3)
3
>>> flatten([0, [1, ["two"]]])
[0, 1, 'two']
>>> flatten( (0, (1, ("two",))) )
(0, 1, 'two')
>>> flatten([0, [1, 2], 3, ([4, 5], 6)])
[0, 1, 2, 3, 4, 5, 6]
>>> flatten( (0, 1, (i + 1 for i in xrange(1, 3)) ) )
(0, 1, 2, 3)
>>> flatten([[[[[0]]]]])
[0]
>>> flatten([0, [[{"a":[["hi"]]}]]])
[0, {'a': [['hi']]}]
"""
if isinstance(x, basestring):
return x
if hasattr(x, "__iter__"):
if hasattr(x, "items"):
return x
else:
return x
is_tuple = isinstance(x, tuple)
# leave exception here unhandled
# if conversion to list fails
x = list(x)
x.reverse()
r = []
while x:
y = x.pop(-1)
if isinstance(y, basestring):
r.append(y)
continue
if hasattr(y, "__iter__"):
if hasattr(y, "items"):
r.append(y)
continue
else:
r.append(y)
continue
# leave exception here unhandled
# if conversion to list fails
y = list(y)
y.reverse()
x.extend(y)
if is_tuple:
return tuple(r)
else:
return r
