Nested Loops in List Comprehensions: Inner Iterator Referencing Outer?

In Python, list comprehensions allow for multiple iterators, enabling the creation of nested loops. However, the question arises whether one iterator in a comprehension can refer to another.

Specifically, consider the syntax:

[x for x in a for a in b]

Where a and b are sequences, and the intention is for the result to be a flattened list. To replicate this behavior in list comprehension format, the following approach is suggested:

[y for x in a for y in x]

This comprehension evaluates the outer loop's iterator (x) in the inner loop's iterator (y), producing a flattened result. For instance, with the input a = [[1, 2], [3, 4]], the result would be [1, 2, 3, 4], as desired.