[Tutor] appending/updating values dict key value pairs

[Sivaram Neelakantan]

On Sun, Jun 23 2013,eryksun  wrote:


[snipped 14 lines]

> The correct syntax is a dict of dicts:
>
>     {'a': {'foo': 1, 'bar': 2, 'offset': 'fff'}}
>
> A dict is something of a resource hog, and it's unordered. Use it as
> the container because it's mutable and lookups are fast, but for the
> values consider using a namedtuple. It has a smaller footprint, and
> it's ordered.
>
>     from collections import namedtuple
>
>     Record = namedtuple('Record', 'foo bar offset')
>
> You can initialize an instance using either positional or keyword arguments:
>
>     data = {
>         'a': Record(1, 2, 0xfff),
>         'b': Record(foo=3, bar=4, offset=0xaaa),
>     }
>
> Access the fields by index or attribute:
>
>     >>> a = data['a']; a[0], a[1], a[2]
>     (1, 2, 4095)
>
>     >>> b = data['b']; b.foo, b.bar, b.offset
>     (3, 4, 2730)
>
> A tuple is immutable, so modifying a field requires a new tuple. Use
> the _replace method:
>
>     >>> data['b'] = data['b']._replace(offset=0xbbb)
>
>     >>> b = data['b']; b.foo, b.bar, b.offset
>     (3, 4, 3003)
>
>
> If you're curious, it's easy to see how namedtuple works:
>
>     >>> Record = namedtuple('Record', 'foo bar offset', verbose=True)
>     class Record(tuple):
>         'Record(foo, bar, offset)'
>
>         __slots__ = ()
>
>         _fields = ('foo', 'bar', 'offset')
>
>         def __new__(_cls, foo, bar, offset):
>             'Create new instance of Record(foo, bar, offset)'
>             return _tuple.__new__(_cls, (foo, bar, offset))

[snipped 6 lines]

Thanks for the explanation, I'd go with namedtuple as recommended.

 sivaram
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