Ron Adam wrote:
> Neil Cerutti wrote:
>> On 2006-10-16, Tim Chase <python.list at tim.thechases.com> wrote:
>>> If you need it in a flat list, rather than as a list of
>>> chunk_size lists (which are handy for iterating over in many
>>> cases), there are ways of obtaining it, such as the hackish
>>>>>>>>> sum([a[i::chunk_size] for i in range(chunk_size)], [])
>>> [1, 4, 7, 10, 2, 5, 8, 3, 6, 9]
>>>>>> There are likely good recipes for flattening a list. I just
>>> happen not to have any at my fingertips.
>>>> Actually, there isn't a good recipe in Python for flattening a
>> list. They all come out tasting like Circus Peanuts (Turkish
>> Delight for you non-Yanks).
>>>>> Here's two that I came up with. They are both very fast compared to
> anything else I've seen. Maybe they won't taste so much like Peanuts.
> :-)
>>> def flatten(L):
> """ Flatten a list in place.
> """
> i = 0
> while i < len(L):
> while type(L[i]) is list:
> L[i:i+1] = L[i]
> i += 1
> return L
>> def sflatten(sequence):
> """ Return a flattened sequence as a list.
> """
> def iterinner(seq):
> for s in seq:
> if hasattr(s, '__iter__'):
> for i in iterinner(s):
> yield i
> else:
> yield s
> return list(iterinner(sequence))
Woops, cut the wrong one... Replace sflatten above with the following.
def flattened(seq):
""" Return a flattened sequence as a list.
"""
def visit(a, x):
for i in x:
if not hasattr(i, '__iter__'):
a.append(i)
else:
visit(a, i)
a = []
visit(a, seq)
return a
>> Cheers,
> Ron Adam
