There is a similar trick that you can use without the walrus operator. I wrote the code many years ago and I am reproducing this from memory, so the code below may be a little off. Define this class:

    class Any:
        def __eq__(self, other):
            self.value = other
            return True

Then you can use an instance of it as the hole in a pattern. My use case was performing peephole optimizations in a simple 6502 assembler. For example, if the LDA operation (load value from memory location into accumulator) occurs twice in a row, the first load is redundant. So I did this test:

    x, y = Any(), Any()
    if L[i:i+2] == [('LDA', x), ('LDA', y)]:
        L[i:i+2] = [('LDA', y.value)]

(Note that the last line changes the length of the list, so it may be slow on large lists.)

I was going to write a blog post about this back then, but I never did. If anyone is interested, I can write it now.