[Tutor] appending/updating values dict key value pairs

[Sivaram Neelakantan]

On Sun, Jun 23 2013,Steven D'Aprano wrote:

> On 23/06/13 19:42, Sivaram Neelakantan wrote:

[snipped 28 lines]

> Python doesn't have structs in the sense you mean. (But see below
> for alternatives.) There is a struct module for working with
> low-level C-style bytes, ints, doubles etc. but that's not what you
> want.
>
> In this case, you can stick with nested dicts:
>
> {'a' : {'foo': 1, 'bar':2, 'offset': 'fff'}}
>
>
> It may be less typing if you use this format:
>
> {'a': dict(foo=1, bar=2, offset='fff'),
>  'b': dict(foo=2, bar=6, offset='fe0'),
>  'c': dict(foo=4, bar=9, offset='d02'),
>  }
>
>
> Instead of working with dicts, it isn't very hard to create your own
> struct-like class:
>
>
> class MyStruct(object):
>     def __init__(self, foo, bar, offset):
>         self.foo = foo
>         self.bar = bar
>         self.offset = offset
>
>
> A little tedious, but it only needs to be done once, then:
>
> {'a': MyStruct(1, 2, 'fff'),
>  'b': MyStruct(2, 6, 'fe0'),
>  'c': MyStruct(4, 9, 'd02'),
>  }
>
> The advantage is that you can both read and write the attributes:
>
> s = MyStruct(4, 9, 'd02')
> s.foo = 42
> print(s.bar)
>
>
> A third alternative is namedtuple, from the collections module.
>
>
> from collections import namedtuple
>
> MyStruct = namedtuple('MyStruct', 'foo bar offset')
> s = MyStruct(4, 9, 'd02')
> print(s.bar)
>
>
> The advantage here is that namedtuple automatically includes extra
> "polish", such as printing nicely. The only negative is that
> namedtuples are immutable: once created, you cannot modify them, you
> have to create a new one:
>
> # this doesn't work
> s.foo = 42
> # instead do this:
> s = MyStruct(42, s.bar, s.offset)
>
>
> This is deliberate, not a bug. But if you can live with that
> limitation of namedtuples, then they are the recommended way to get
> the equivalent of a Pascal record or C struct. Otherwise just create
> a quick little class as needed.

Thank you for explaining the options, I'd probably go with namedtuple
as it seems to match my needs and I don't want to work on OO/Classes
for now.  I'll read up on the documentation for namedtuple.

 sivaram
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