DaS

Dictionary As Struct

Getting started

Basic Usage

Creating a struct from a standard python dictionary is simply done by using the das.Struct class.

For the most part, the available instance methods are identical to python's dict class, but for the fact that method names that conflict with field names will be renamed with a leading _ (a warning message will be issued once then)

>>> import das
>>> 
>>> s = das.Struct({"group": {"field1": [0, 1, 2], "field2": "aaa"},
...                 "field4": 3.0,
...                 "field5": "bbb"})
>>> s.group.field1.append(10)
>>> print(s)
{'group': {'field2': 'aaa', 'field1': [0, 1, 2, 10]}, 'field4': 3.0, 'field5': 'bbb'}

das has a utility pretty print function pprint too

>>> das.pprint(s)
{
  'field4': 3.0,
  'field5': 'bbb',
  'group': {
    'field1': [
      0,
      1,
      2,
      10
    ],
    'field2': 'aaa'
  }
}

One can also easily serialize/deserialize struct content to file

>>> das.write(s, "/path/to/file.ext")
>>> s2 = das.read("/path/to/file.ext")
>>> das.pprint(s2)
{
  'field4': 3.0,
  'field5': 'bbb',
  'group': {
    'field1': [
      0,
      1,
      2,
      10
    ],
    'field2': 'aaa'
  }
}

Advanced Usage

Type validation

Schema

tests/test005/shopping.schema

{
  "currency_names": String(default="Yen", choices=["Yen", "Euro", "Dollar"]),

  "item": Struct(name=String(),
                 value=Real(min=0.0),
                 currency=SchemaType("currency_names"),
                 description=String()),

  "basket": Struct(items=Sequence(type=SchemaType("item")))
}

Schema module & mixins

tests/test005/shopping.py

import das

CurrencyRates = {"yen": 110.30,
                 "euro": 0.81,
                 "dollar": 1}
DefaultCurrency = "yen"

def get_currency_key(currency):
  ck = currency
  if not ck in CurrencyRates:
    ck = ck.lower()
    if not ck in CurrencyRates and ck.endswith("s"):
      ck = ck[:-1]
  return (ck if ck in CurrencyRates else None)

def is_currency_supported(currency):
  return (get_currency_key(currency) is not None)

def get_currency_rate(currency):
  return CurrencyRates.get(get_currency_key(currency), 0.0)

def convert_currencies(amount, source_currency, destination_currency):
  fc = get_currency_key(source_currency)
  tc = get_currency_key(destination_currency)
  if fc is None or tc is None:
    raise Exception("Invalid currency conversion: %s -> %s" % (source_currency, destination_currency))
  return (amount * CurrencyRates[tc] / CurrencyRates[fc])


class Item(das.Mixin):
  @classmethod
  def get_schema_type(klass):
    return "shopping.item"

  def __init__(self, *args, **kwargs):
    super(Item, self).__init__(*args, **kwargs)

  def value_in(self, currency=DefaultCurrency):
    return convert_currencies(self.value, self.currency, currency)
    

class Basket(das.Mixin):
  @classmethod
  def get_schema_type(klass):
    return "shopping.basket"

  def __init__(self, *args, **kwargs):
    super(Basket, self).__init__(*args, **kwargs)

  def value_in(self, currency=DefaultCurrency):
    return reduce(lambda x, y: x + y.value_in(currency), self.items, 0.0)


das.register_mixins(Item, Basket)

Usage

$ export DAS_SCHEMA_PATH=directory/of/shopping.schema
$ python
>>> import das
>>> b = das.make_default("shopping.basket")
>>> b.items.append(das.make("shopping.item", name="carottes", value=110))
>>> b.items.append(das.make("shopping.item", name="meat", value=320))
>>> das.pprint(b)
{
  'items': [
    {
      'currency': 'Yen',
      'description': '',
      'name': 'carottes',
      'value': 110.0
    },
    {
      'currency': 'Yen',
      'description': '',
      'name': 'meat',
      'value': 320.0
    }
  ]
}
>>> for c in ["yen", "euro", "dollar"]:
...   print("%f %s(s)" % (b.value_in(c), c))
430.000000 yen(s)
3.157752 euro(s)
3.898459 dollar(s)

Built-in schema types

1. Boolean
2. Integer
3. Real
4. String
5. Tuple
6. Sequence
7. Struct
8. Dict
9. SchemaType
10. Class

Required methods:

• copy() -> instance
• __repr__() -> str (use when serializing)

repr should return a class instanciating call

• __cmp__() -> -1, 0 or 1 (use when comparing data sets)

Optional methods:

• string_to_value(str) -> noreturn (used by the editor)
• value_to_string() -> str (used by the editor)

11. Or
12. Optional
13. Empty
14. Deprecated

Mixins

Developing

Run unit tests

Running the command

python tests/run.py

in top level directory will execute all registered tests within the 'tests' folder.

Staging package

Running the command

scons

in top level directory will create a simple package distribution folder within the top level directory 'release' folder.

Creating Ecosystem distribution

Run the command

scons eco

in top level directory will create Ecosystem distribution in top level directory 'eco' folder. To specify a custom defined directory, use the eco-dir= flag

scons eco eco-dir=path/to/target/directory

TODO

• Implemente copy-paste
• Allow multiple items drag'n'drop
• Add a toolbar class (open/save/save as, copy/cut/paste, undo/redo)