idiom for initial list of lists

[Pekka Pessi]

In message <Pine.LNX.4.21.0009081645290.1107-100000 at fep132.fep.ru> Oleg Broytmann <phd at phd.russ.ru> writes:
>> so I'm forced to use the rather pedantic
>> S=[]
>> for i in range(n): S[i].append([])

>   That's the only and one correct way.

        I prefer list():

>>> a = map(list, 5 * [[]])
>>> a[0].append(1)
>>> a
[[1], [], [], [], []]

        or 

>>> a = map(list, 5 * ((),))
>>> a
[[], [], [], [], []]
>>> a[0].append(1)
>>> a
[[1], [], [], [], []]

                                        Pekka