GeezerVison

PicklerMemoProxy.copy/2505entries: Mean +- std dev: [base] 136 us +- 4 us -> [opt] 133 us +- 5 us: 1.02x faster
PicklerMemoProxy.copy/50005entries: Mean +- std dev: [base] 4.57 ms +- 0.06 ms -> [opt] 4.52 ms +- 0.05 ms: 1.01x faster

Geometric mean: 1.02x faster

import io
import pickle
import pyperf


def make_proxy(n):
    buf = io.BytesIO()
    pk = pickle.Pickler(buf, protocol=pickle.HIGHEST_PROTOCOL)
    data = [object() for _ in range(n)]
    nested = {i: [object(), object()] for i in range(n // 2)}
    pk.dump(data)
    pk.dump(nested)
    proxy = pk.memo  # PicklerMemoProxy
    # Keep a reference to the source pickler alive via closure.
    return pk, proxy


def main():
    runner = pyperf.Runner()

    for n in (1000, 20000):
        pk, proxy = make_proxy(n)
        entries = len(proxy.copy())
        runner.bench_func(
            f"PicklerMemoProxy.copy/{entries}entries",
            proxy.copy,
        )


if __name__ == "__main__":
    main()