tuple unpacking is slower than tuple(list comprehension)

Feature or enhancement

Proposal:

In []: %timeit (*(x**2 for x in range(1000)),)  # (A)
47.2 μs ± 1.18 μs per loop (mean ± std. dev. of 7 runs, 10,000 loops each)

In []: %timeit tuple(x**2 for x in range(1000))  # most idiomatic
45.4 μs ± 5.57 μs per loop (mean ± std. dev. of 7 runs, 10,000 loops each)

In []: %timeit (*[x**2 for x in range(1000)],)  # (B)
36.5 μs ± 77.8 ns per loop (mean ± std. dev. of 7 runs, 10,000 loops each)

In []: %timeit tuple([x**2 for x in range(1000)])  # fastest
33.8 μs ± 710 ns per loop (mean ± std. dev. of 7 runs, 10,000 loops each)

Currently (A) and (B) are slower than the last one, even though it doesn't need to be so. There doesn't seem to be any bottleneck such as global namespace lookup.

Also, we want people to write the most idiomatic code, so it would be preferable to make the most idiomatic version to be as fast as the fastest version. Possibly with something like

if tuple is builtins.tuple:
    MAGIC
else:
    code as usual...

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-149960

Inizia riproducendo le quattro espressioni di benchmark dell’issue e confronta l’unpacking delle tuple con la costruzione di tuple. Esamina la PR collegata gh-149960 per verificare il lavoro già in corso; il lavoro è completato quando la forma idiomatica con generatore non è più indietro rispetto alla forma più veloce senza rompere il comportamento di fallback indicato.