On Aug 1, 2012, at 1:46 AM, Mark Shannon wrote:

'''
Being able to pre-allocate lists based on the expected size, as estimated by __length_hint__,
can be a significant optimization.
PyPy has been observed to run some code slower than CPython, purely because this optimization is absent.
'''

Which is a PyPy bug report, not a rationale for a PEP ;)

Alex's rationale is correct and well expressed.

Your proposed revision reflects fuzzy thinking about why __length_hint__ is useful.

Regardless of resizing growth factors, it is *always* helpful to know how much

memory to allocate. Calls to the allocators (especially for large blocks)

and possible the recopying of data should be avoided when possible.

Raymond