I just discovered that the assignment operator leaks variables out of comprehensions.

>>> [(j:=i*i)+1/j for i in range(1, 3)]
[2.0, 4.25]
>>> j
4
>>> g = ((j:=i*i*i)+1/j for i in range(1, 3))
>>> list(g)
[2.0, 8.125]
>>> j
8

So it does not supersedes this optimization.