Compromise: Datatypes for Reasonable People

PyCon 2016 Lightning Talk

Should array indices start at 0 or 1? My compromise of 0.5 was rejected without, I thought, proper consideration.

—Stan Kelly-Bootle

In a world of disagreement, Compromise is everything for everyone. You no longer have to make the tough decisions in life.

>>> l = HalfIndexList('abcde')
>>> l[0.5]
'a'
>>> l[1.5]
'b'
>>> l[-0.5]
'e'
>>> l.reverse()
>>> l
['e', 'd', 'c', 'b', 'a']

Some may find having a set starting index a bit restrictive. They should use FlexibleList.

>>> l = FlexibleList('abcde')
FlexibleList(['a', 'b', 'c', 'd', 'e'], start=0)
>>> l.start = 5
>>> l[7]
'c'

SemiMutableSequences can't be changed.

>>> t = SemiMutableSequence(range(5))
>>> t
SemiMutableSequence([0, 1, 2, 3, 4])
>>> t[1] = 7
TypeError: SemiMutableSequence object does not support item assignment

Unless you, like, really want to.

>>> t = SemiMutableSequence(range(5))
>>> try:
...     t[1] = 7
... except TypeError:
...     pass
>>> t[1] = 7
>>> t
SemiMutableSequence([0, 7, 2, 3, 4])

But why should you be limited to a single attempt? Try a few times. If you really want mutability, you have to work for it.

>>> t = SemiMutableSequence(range(5), times=5)
>>> for _ in range(4):
...     try:
...         t[1] = 7
...     except TypeError:
...         pass
>>> t[1] = 7
>>> t
SemiMutableSequence([0, 7, 2, 3, 4])

Magic Numbers are bad. Who could possibly understand what this means?

>>> feet = yards * 3

These should be replaced by Number instances.

>>> from compromise import THREE
>>> feet = yards * THREE

See? Much better. You can make longer numbers with & and floats with point()

>>> ONE & ZERO
10
>>> THREE + point(ONE & FOUR)
3.14

They're constant by convention only. Don't change them!

>>> TWO = (ONE & ZERO) / FOUR
>>> TWO + TWO
5

Or change them if you want. I don't care.