Create a list of empty dictionaries

Question

I want to create a list of variable length containing empty directories.

n = 10 # size of list
foo = []
for _ in range(n)
    foo.append({})

Would you do this the same way, or is there something like?

a = [{}*n]

Answer 1

List comprehensions to the rescue!

foo = [{} for _ in range(n)]

There is no shorter notation, I am afraid. In Python 2 you use xrange(n) instead of range(n) to avoid materializing a useless list.

The alternative, [{}] * n creates a list of length n with only one dictionary, referenced n times. This leads to nasty surprises when adding keys to the dictionary.