Skip deepcopy memo check when memo is empty

[eendebakpt]

Feature or enhancement

Proposal:

In the copy.deepcopy method we can skip the initial memo check if the memo was just created. We can replace

    if memo is None:
        memo = {}
    d = id(x)
    y = memo.get(d, _nil)
    if y is not _nil:
        return y

with

    d = id(x)
    if memo is None:
        memo = {}
    else:
        y = memo.get(d, _nil)
        if y is not _nil:
            return y

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-109868: Skip deepcopy memo check for empty memo #109869