Initialise a list to a specific length in Python

list multiplication works.

>>> [0] * 10
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

If the "default value" you want is immutable, @eduffy's suggestion, e.g. [0]*10, is good enough.

But if you want, say, a list of ten dicts, do not use [{}]*10 -- that would give you a list with the same initially-empty dict ten times, not ten distinct ones. Rather, use [{} for i in range(10)] or similar constructs, to construct ten separate dicts to make up your list.