Not the same kind of nesting, is it?

  [[None for _y in range(y)] for _x in range(x)]

for two dimensions is fine, while

  [None for _x in range(x) for _y in range(y)]

(to create a flattened 2-dim list? excuse the dummy example) is just begging for later headache. Explicit looping is much more readable. Note the flipped order of expressions -- these two statements create the same iterators.

Not to mention, you can even reuse the name for extra evil:

  [i for i in range(2) for i in range(3)]

results in

  [0, 1, 2, 0, 1, 2]

Fwiw, I find creating a 2d array and then flattening (`itertools.chain.from_iterable([[None for _y in range(y)] for _x in range(x)])` to be both readable and reasonably concise, though yes explicit loops are also fine.

nice trick.. though if you are relying on the 'generator' aspect of comprehensions this may be problematic (will create in-memory copies)