Rationale for core Python numeric types

Tim Peters tim.peters at gmail.com
Thu Jul 15 21:14:47 CEST 2004


[Tim Peters]
>> You're too worried.  The only real semantic difference is that
>> a left shift won't throw away bits by magic, and in a
>> platform-dependent way, anymore.

[Grant Edwards]
> How does the 1's compliment operator know how many bits to
> return?  IOW, what is ~0 going to be?

Python longs are 2's-complement with a conceptually infinite number of
sign bits (whether 0 or 1).  So ~0 will be, like ~0L today, an
infinite string of 1 bits.  Even today:

>>> (~0) & 0xff
255
>>> (~0L) & 0xff
255L
>>> ~0 == ~0L == -1
True
>>>

> For much of what I do with Python, fixed width integers would
> be awfully nice -- then I wouldn't have to and everything with
> 0xff, 0xffff, or 0xffffffff to get the results I want.

Nothing about that is planned to change (there are no plans to add
fixed-width ints).  I don't think there's even a PEP on the topic
(although I may be wrong about that -- I want them so little I may not
remember such a PEP if it exists).



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