New submission from Raymond Hettinger:
The current 'b' formatting code in inconvenient for emulating, demonstrating,
and teaching two's complement arithmetic. The problem is that negative inputs
are always formatted with a minus sign. I propose that some formatting code be
provided for fixed-width display where the leading bit is a sign bit.
For example, if code were a capital 'B' and the total width were 8-bits:
>>> x = -12
>>> format(12, '08B')
'11110100'
Currently, to achieve the same effect, one of the following is used:
>>> format(x if x >= 0 else x + 2**8, '08b')
'11110100'
or
>>> format(x & (2**8 - 1), '08b')
'11110100'
For values outside the valid range, perhaps a ValueError could be raised:
>>> format(-200, '08B')
Traceback (most recent call last):
...
ValueError: Expected value in range -128 <= x < 128, not -200
I'm not sure what the right code should be. The idea of capital 'B' is
attractive, but we already have a different relationship between 'X' and 'x'.
There could also be a modifier symbol such as '!' in '!8b'.
----------
components: Interpreter Core
messages: 295162
nosy: mark.dickinson, rhettinger, talin
priority: low
severity: normal
status: open
title: Add integer formatting code for fixed-width signed arithmetic (2's
complement)
type: enhancement
versions: Python 3.7
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Python tracker <[email protected]>
<http://bugs.python.org/issue30571>
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