lexicon 0.1.0

## WHAT

Lexicon is a simple collection of `dict` subclasses providing extra power:

* `AliasDict`, a dictionary supporting both simple and complex key aliasing:
* Alias a single key to another key, so that e.g. `mydict['bar']` points to
`mydict['foo']`, for both reads and writes.
* Alias a single key to a list of other keys, for writing only, e.g. with
`active_groups = AliasDict({'ops': True, 'biz': True, 'dev': True,
'product': True})` one can make an alias `'tech'` mapping to `('ops',
'dev')` and then e.g. `active_groups['tech'] = False`.
* Aliasing is recursive: an alias pointing to another alias will behave as
if it points to the other alias' target.
* `AttributeDict`, supporting attribute read & write access, e.g.
`mydict = AttributeDict({'foo': 'bar'})` exhibits `mydict.foo` and
`mydict.foo = 'new value'`.
* `Lexicon`, a subclass of both of the above which exhibits both sets of
behavior.

## HOW

* `pip install lexicon`
* `from lexicon import Lexicon` (or one of the superclasses)
* Use as needed.

You can install the [development
version](https://github.com/bitprophet/lexicon/tarball/master#egg=lexicon-dev)
via `pip install lexicon==dev`.

## API

### `AliasDict`

In all examples, `'myalias'` is the alias and `'realkey'` is the "real",
unaliased key.

* `alias(from_='myalias', to='realkey')`: Alias `myalias` to `realkey` so
`d['myalias']` behaves exactly like `d['realkey']` for both reads and writes.
See below for details on how an alias affects other dict operations.
* `alias(from_='myalias', to=('realkey', 'otherrealkey'))`: Alias `myalias` to
both `realkey` and `otherrealkey`. As you might expect, this only works well
for writes, as there is never any guarantee that all targets of the alias
will contain the same value.
* `unalias(from_='myalias')`: Removes the `myalias` alias; any subsequent
reads/writes to `myalias` will behave as normal for a regular `dict`.
* `'myalias' in d` (aka `__contains__`): Returns True when given an alias, so
if `myalias` is an alias to some other key, dictionary membership tests will
behave as if `myalias` is set.
* `del d['myalias']` (aka `__delitem__`): This effectively becomes `del
d['realkey']` -- to remove the alias itself, use `unalias()`.
* `del d['realkey']`: Deletes the real key/value pair (i.e. it calls
`dict.__del__`) but doesn't touch any aliases pointing to `realkey`.
* As a result, "dangling" aliases pointing to nonexistent keys will raise
`KeyError` on access, but will continue working if the target key is
repopulated later.

Caveats:

* Because of the single-key/multi-key duality, `AliasDict` is incapable of
honoring non-string-type keys when aliasing (it must test `isinstance(key,
basestring)` to tell strings apart from non-string iterables).
* `AliasDict` instances may still *use* non-string keys, of course -- it
just can't use them as alias targets.

### `AttributeDict`

* `d.key = 'value'` (aka `__setattr__`): Maps directly to `d['key'] = 'value'`.
* `d.key` (aka `__getattr__`): Maps directly to `d['key']`.
* `del d.key` (aka `__delattr__`): Maps directly to `del d['key']`.
* Collisions between "real" or pre-existing attributes, and
attributes-as-dict-keys, always results in the real attribute winning. Thus
it isn't possible to use attribute access to access e.g. `d['get']`.

### `Lexicon`

Lexicon subclasses from `AttributeDict` first, then `AliasDict`, with the end
result that attribute access will honor aliases. E.g.:

d = Lexicon()
d.alias('myalias', to='realkey')
d.myalias = 'foo'
print d.realkey # prints 'foo'