Metadata-Version: 1.1
Name: tri.declarative
Version: 0.21.0
Summary: tri.declarative contains class decorators to define classes with subclass semantics in the style of django Model classes.
Home-page: UNKNOWN
Author: Johan Lübcke
Author-email: johan.lubcke@trioptima.com
License: BSD
Description: .. image:: https://travis-ci.org/TriOptima/tri.declarative.svg?branch=master
            :target: https://travis-ci.org/TriOptima/tri.declarative
        .. image:: http://codecov.io/github/TriOptima/tri.declarative/coverage.svg?branch=master
            :target: http://codecov.io/github/TriOptima/tri.declarative?branch=master
            
        tri.declarative
        ===============
        
        tri.declarative contains tools that make it easy to write declarative code. This includes:
        
        - `class decorators`_ to define classes with subclass semantics in the style of django Model classes
        - recursively evaluating_ embedded lambda expressions in complex data structures
        - recursively filtering_ of complex data structures
        - `keyword argument dispatching`_
        - `get/set attribute given a path string`_ (e.g. 'foo__bar__baz')
        
        
        Class decorators
        ----------------
        
        With just a few lines of code, turn your API from:
        
        .. code-block:: python
        
            quux = Foo(things=[Bar(name='a', param=1), Bar(name='b', param=2), Bar(name='c', param=2)], baz=3)
        
        into:
        
        .. code-block:: python
        
            class Quux(Foo):
                a = Bar(param=1)
                b = Bar(param=2)
                c = Bar(param=2)
        
                class Meta:
                    baz = 3
        
        And you can still use the first style when it's more convenient!
        
        More detailed usage examples on `@declarative`_ below.
        
        
        Evaluating
        ----------
        
        .. code-block:: python
        
            d = dict(
                foo=lambda x: x*2,
                bar=lambda y: y+5,
                baz=[
                    foo=lambda x: x*6,
                ],
            )
        
            # evaluate only one level
            assert evaluate(d, x=2) == dict(
                foo=4,
                bar=lambda y: y+5,  # this function doesn't match the signature so isn't evaluated
                baz=[
                    foo=lambda x: x*6,  # one level down so isn't evaluated
                ],
            )
        
            # evaluate recursively
            assert evaluate_recursive(d, x=2) == dict(
                foo=4,
                bar=lambda y: y+5,  # this function doesn't match the signature so isn't evaluated
                baz=[
                    foo=12,
                ],
            )
        
        
        Filtering
        ---------
        
        .. code-block:: python
        
            d = dict(
                foo=dict(
                    show=False,
                    x=1,
                ),
                bar=dict(
                    show=True,
                    x=2,
                ),
            )
        
            assert filter_show_recursive(d) == dict(
                bar=dict(
                    show=True,
                    x=2,
                ),
            )
        
        
        Keyword argument dispatching
        ----------------------------
        
        setdefaults, collect_namespaces and assert_kwargs_empty:
        
        .. code-block:: python
        
            def foo(**kwargs):
                setdefaults(kwargs, dict(
                    bar__baz=3,
                    bar__qwe=5,
                    baz__asd=2,
                ))
                kwargs = collect_namespaces(kwargs)
                bar(**kwargs.pop('bar', {}))
                baz(**kwargs.pop('baz', {}))
                assert_kwargs_empty(kwargs)
        
        Get/set attribute given a path string
        -------------------------------------
        
        .. code-block:: python
        
            class Foo(object):
                def __init__(a):
                    self.a = a
        
            class Bar(object):
                def __init__(b):
                    self.b = b
        
            class Baz(object):
                def __init__(c):
                    self.c = c
        
            x = Foo(Bar(Baz(c=3)))
        
            assert getattr_path(x, 'a__b__c') == 3
            assert setattr_path(x, 'a__b__c', 10)
            assert getattr_path(x, 'a__b__c') == 10
        
        
        Running tests
        -------------
        
        You need tox installed then just `make test`.
        
        
        License
        -------
        
        BSD
        
        
        Documentation
        -------------
        
        https://trideclarative.readthedocs.org.
        
        
        Usage
        =====
        
        
        @declarative
        ------------
        
        In the example below, the :code:`@declarative(str)` decorator will ensure that all :code:`str` members of class Foo will be
        collected and sent as :code:`members` constructor keyword argument.
        
        .. code-block:: python
        
            from tri.declarative import declarative
        
            @declarative(str)
            class Foo(object):
                bar = 'barbar'
                baz = 'bazbaz'
                boink = 17
        
                def __init__(self, members):
                    assert members['bar'] == 'barbar'
                    assert members['baz'] == 'bazbaz'
                    assert 'boink' not in members
        
            f = Foo()
        
        The value of the :code:`members` argument will also be collected from sub-classes:
        
        .. code-block:: python
        
            from tri.declarative import declarative
        
            @declarative(str)
            class Foo(object):
        
                def __init__(self, members):
                    assert members['bar'] == 'barbar'
                    assert members['baz'] == 'bazbaz'
        
            class MyFoo(Foo):
                bar = 'barbar'
                baz = 'bazbaz'
        
                def __init__(self):
                    super(MyFoo, self).__init__()
        
            f = MyFoo()
        
        
        The :code:`members` argument can be given another name (:code:`things` in the example below).
        
        .. code-block:: python
        
            from tri.declarative.declarative import declarative
        
            @declarative(str, 'things')
            class Foo(object):
        
                bar = 'barbar'
        
                def __init__(self, **kwargs):
                    assert 'things' in kwargs
                    assert kwargs['things']['bar'] == 'barbar'
        
            f = Foo()
        
        
        Note that the collected dict is an :code:`OrderedDict` and will be ordered by class inheritance and by using
        :code:`sorted` of the values within each class. (In the 'str' example, :code:`sorted` yields in alphabetical order).
        
        Also note that the collection of *class* members based on their class does *not* interfere with *instance* constructor
        argument of the same type.
        
        .. code-block:: python
        
            from tri.declarative import declarative
        
            @declarative(str)
            class Foo(object):
                charlie = '3'
                alice = '1'
        
                def __init__(self, members):
                    assert members == OrderedDict([('alice', '1'), ('charlie', '3'),
                                                   ('bob', '2'), ('dave', '4'),
                                                   ('eric', '5')])
                    assert 'animal' not in members
        
        
            class MyFoo(Foo):
                dave = '4'
                bob = '2'
        
            class MyOtherFoo(MyFoo):
                eric = '5'
        
                def __init__(self, animal)
                    assert animal == 'elephant'
        
            f = MyOtherFoo('elephant')
        
        
        @creation_ordered
        -----------------
        
        Class decorator that ensures that instances will be ordered after creation order when sorted.
        
        This is useful for classes intended to be used as members of a :code:`@declarative` class when member order matters.
        
        .. code-block:: python
        
            from tri.declarative import creation_ordered
        
            @creation_ordered
            class Thing(object):
                pass
        
            t1 = Thing()
            t2 = Thing()
            t3 = Thing()
        
            assert sorted([t2, t3, t1]) == [t1, t2, t3]
        
        
        Real world use-case
        -------------------
        
        Below is a more complete example of using @declarative:
        
        .. code-block:: python
        
            from tri.declarative import declarative, creation_ordered
        
        
            @creation_ordered
            class Field(object):
                pass
        
        
            class IntField(Field):
                def render(self, value):
                    return '%s' % value
        
        
            class StringField(Field):
                def render(self, value):
                    return "'%s'" % value
        
        
            @declarative(Field, 'table_fields')
            class SimpleSQLModel(object):
        
                def __init__(self, **kwargs):
                    self.table_fields = kwargs.pop('table_fields')
        
                    for name in kwargs:
                        assert name in self.table_fields
                        setattr(self, name, kwargs[name])
        
                def insert_statement(self):
                    return 'INSERT INTO %s(%s) VALUES (%s)' % (self.__class__.__name__,
                                                             ', '.join(self.table_fields.keys()),
                                                             ', '.join([field.render(getattr(self, name))
                                                                        for name, field in self.table_fields.items()]))
        
        
            class User(SimpleSQLModel):
                username = StringField()
                password = StringField()
                age = IntField()
        
        
            my_user = User(username='Bruce_Wayne', password='Batman', age=42)
            assert my_user.username == 'Bruce_Wayne'
            assert my_user.password == 'Batman'
            assert my_user.insert_statement() == "INSERT INTO User(username, password, age) VALUES ('Bruce_Wayne', 'Batman', 42)"
        
            # Fields are ordered by creation time (due to having used the @creation_ordered decorator)
            assert my_user.get_meta().table_fields.keys() == ['username', 'password', 'age']
        
        
        @with_meta
        ----------
        
        Class decorator to enable a class (and it's sub-classes) to have a 'Meta' class attribute.
        
        The members of the Meta class will be injected as arguments to constructor calls. e.g.:
        
        .. code-block:: python
        
            from tri.declarative import with_meta
        
            @with_meta
            class Foo(object):
        
                class Meta:
                    foo = 'bar'
        
                def __init__(self, foo, buz):
                    assert foo == 'bar'
                    assert buz == 'buz'
        
            foo = Foo(buz='buz')
        
            # Members of the 'Meta' class can be accessed thru the get_meta() class method.
            assert foo.get_meta() == {'foo': 'bar'}
            assert Foo.get_meta() == {'foo': 'bar'}
        
            Foo()  # Crashes, has 'foo' parameter, but no has no 'buz' parameter.
        
        
        The passing of the merged name space to the constructor is optional.
        It can be disabled by passing :code:`add_init_kwargs=False` to the decorator.
        
        .. code-block:: python
        
            from tri.declarative import with_meta
        
            @with_meta(add_init_kwargs=False)
            class Foo(object):
                class Meta:
                    foo = 'bar'
        
            Foo()  # No longer crashes
            assert Foo().get_meta() == {'foo': 'bar'}
        
        
        Another example:
        
        .. code-block:: python
        
            from tri.declarative import with_meta
        
            class Foo(object):
        
                class Meta:
                    foo = 'bar'
                    bar = 'bar'
        
            @with_meta
            class Bar(Foo):
        
                class Meta:
                    foo = 'foo'
                    buz = 'buz'
        
                def __init__(self, *args, **kwargs):
                    assert kwargs['foo'] == 'foo'  # from Bar (overrides Foo)
                    assert kwargs['bar'] == 'bar'  # from Foo
                    assert kwargs['buz'] == 'buz'  # from Bar
        
        
        This can be used e.g to enable sub-classes to modify constructor default arguments.
        
        
        Changelog
        =========
        
        
        0.21.0 (2016-03-01)
        ~~~~~~~~~~~~~~~~~~~
        
        * Fix corner case in collect_namespaces where one parameter imply a value and
          others imply a namespace.
        
        * Added `setdefaults_path` helper with `__` namespace traversal.
        
        
        0.20.0 (2016-02-29)
        ~~~~~~~~~~~~~~~~~~~
        
        * Added `assert_kwargs_not_empty` convenience function.
        
        * Improved documentation.
        
        
        0.19.0 (2016-01-12)
        ~~~~~~~~~~~~~~~~~~~
        
        * When making instances of a class decorated with `@declarative` the declared
          values are copied (shallow) before being passed to `__init__`.
        
        * Instances will get an own copy of the declared attributes written to their
          `__dict__`
        
        
Keywords: tri.declarative
Platform: UNKNOWN
Classifier: Development Status :: 4 - Beta
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: BSD License
Classifier: Natural Language :: English
Classifier: Programming Language :: Python :: 2
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3.5
