tuple unpacking is slower than tuple(list comprehension) #138325
Description
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