[[[foo(x) for x in y] for y in bar_vec if baz(y)] for bar_vec in bar_mat if bar_vec != []]Also, another way to write this (which results in a flattened list) is:
[foo(x) for bar_vec in bar_mat for y in bar_vec if baz(y) for x in y] for bar_vec in bar_mat:
if bar_vec != []:
for y in bar_vec:
if baz(y):
for x in y:
foo(x)
But if there is anyone coming after me, I would write it in this style for their sake, because this style is easier to change.
[foo(x) for x in nonempty(bar_mat)]
I mean, it's not the clearest thing to read but labeling it horrible seems to be a judgement call that's unwarranted. And as software developers, we should create an environment that's less hostile to people who write things in ways we wouldn't.
And honestly, that set of list comprehensions has a bit of a lispy functional vibe, which could quite frankly be applauded in certain contexts.