How do I efficiently filter computed values within a Python list comprehension?

Question

The Python list comprehension syntax makes it easy to filter values within a comprehension. For example:

result = [x**2 for x in mylist if type(x) is int]
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Answer 1

Came up with my own answer after a minute of thought. It can be done with nested comprehensions:

result = [y for y in (expensive(x) for x in mylist) if y]

I guess that works, though I find nested comprehensions are only marginally readable