collections.py

SQLAlchemy. 经典的Python ORM框架。学习必看。

    def clear(fn):
        def clear(self):
            for key in self:
                __del(self, self[key])
            fn(self)
        _tidy(clear)
        return clear

    def pop(fn):
        def pop(self, key, default=Unspecified):
            if key in self:
                __del(self, self[key])
            if default is Unspecified:
                return fn(self, key)
            else:
                return fn(self, key, default)
        _tidy(pop)
        return pop

    def popitem(fn):
        def popitem(self):
            __before_delete(self)
            item = fn(self)
            __del(self, item[1])
            return item
        _tidy(popitem)
        return popitem

    def setdefault(fn):
        def setdefault(self, key, default=None):
            if key not in self:
                self.__setitem__(key, default)
                return default
            else:
                return self.__getitem__(key)
        _tidy(setdefault)
        return setdefault

    if sys.version_info < (2, 4):
        def update(fn):
            def update(self, other):
                for key in other.keys():
                    if key not in self or self[key] is not other[key]:
                        self[key] = other[key]
            _tidy(update)
            return update
    else:
        def update(fn):
            def update(self, __other=Unspecified, **kw):
                if __other is not Unspecified:
                    if hasattr(__other, 'keys'):
                        for key in __other.keys():
                            if key not in self or self[key] is not __other[key]:
                                self[key] = __other[key]
                    else:
                        for key, value in __other:
                            if key not in self or self[key] is not value:
                                self[key] = value
                for key in kw:
                    if key not in self or self[key] is not kw[key]:
                        self[key] = kw[key]
            _tidy(update)
            return update

    l = locals().copy()
    l.pop('_tidy')
    l.pop('Unspecified')
    return l

def _set_decorators():
    """Hand-turned instrumentation wrappers that can decorate any set-like
    sequence class."""

    def _tidy(fn):
        setattr(fn, '_sa_instrumented', True)
        fn.__doc__ = getattr(getattr(Set, fn.__name__), '__doc__')

    Unspecified=object()

    def add(fn):
        def add(self, value, _sa_initiator=None):
            __set(self, value, _sa_initiator)
            # testlib.pragma exempt:__hash__
            fn(self, value)
        _tidy(add)
        return add

    if sys.version_info < (2, 4):
        def discard(fn):
            def discard(self, value, _sa_initiator=None):
                if value in self:
                    self.remove(value, _sa_initiator)
            _tidy(discard)
            return discard
    else:
        def discard(fn):
            def discard(self, value, _sa_initiator=None):
                # testlib.pragma exempt:__hash__
                if value in self:
                    __del(self, value, _sa_initiator)
                    # testlib.pragma exempt:__hash__
                fn(self, value)
            _tidy(discard)
            return discard

    def remove(fn):
        def remove(self, value, _sa_initiator=None):
            # testlib.pragma exempt:__hash__
            if value in self:
                __del(self, value, _sa_initiator)
            # testlib.pragma exempt:__hash__
            fn(self, value)
        _tidy(remove)
        return remove

    def pop(fn):
        def pop(self):
            __before_delete(self)
            item = fn(self)
            __del(self, item)
            return item
        _tidy(pop)
        return pop

    def clear(fn):
        def clear(self):
            for item in list(self):
                self.remove(item)
        _tidy(clear)
        return clear

    def update(fn):
        def update(self, value):
            for item in value:
                if item not in self:
                    self.add(item)
        _tidy(update)
        return update

    def __ior__(fn):
        def __ior__(self, value):
            if sautil.duck_type_collection(value) is not Set:
                return NotImplemented
            for item in value:
                if item not in self:
                    self.add(item)
            return self
        _tidy(__ior__)
        return __ior__

    def difference_update(fn):
        def difference_update(self, value):
            for item in value:
                self.discard(item)
        _tidy(difference_update)
        return difference_update

    def __isub__(fn):
        def __isub__(self, value):
            if sautil.duck_type_collection(value) is not Set:
                return NotImplemented
            for item in value:
                self.discard(item)
            return self
        _tidy(__isub__)
        return __isub__

    def intersection_update(fn):
        def intersection_update(self, other):
            want, have = self.intersection(other), Set(self)
            remove, add = have - want, want - have

            for item in remove:
                self.remove(item)
            for item in add:
                self.add(item)
        _tidy(intersection_update)
        return intersection_update

    def __iand__(fn):
        def __iand__(self, other):
            if sautil.duck_type_collection(other) is not Set:
                return NotImplemented
            want, have = self.intersection(other), Set(self)
            remove, add = have - want, want - have

            for item in remove:
                self.remove(item)
            for item in add:
                self.add(item)
            return self
        _tidy(__iand__)
        return __iand__

    def symmetric_difference_update(fn):
        def symmetric_difference_update(self, other):
            want, have = self.symmetric_difference(other), Set(self)
            remove, add = have - want, want - have

            for item in remove:
                self.remove(item)
            for item in add:
                self.add(item)
        _tidy(symmetric_difference_update)
        return symmetric_difference_update

    def __ixor__(fn):
        def __ixor__(self, other):
            if sautil.duck_type_collection(other) is not Set:
                return NotImplemented
            want, have = self.symmetric_difference(other), Set(self)
            remove, add = have - want, want - have

            for item in remove:
                self.remove(item)
            for item in add:
                self.add(item)
            return self
        _tidy(__ixor__)
        return __ixor__

    l = locals().copy()
    l.pop('_tidy')
    l.pop('Unspecified')
    return l


class InstrumentedList(list):
    """An instrumented version of the built-in list."""

    __instrumentation__ = {
       'appender': 'append',
       'remover': 'remove',
       'iterator': '__iter__', }

class InstrumentedSet(Set):
    """An instrumented version of the built-in set (or Set)."""

    __instrumentation__ = {
       'appender': 'add',
       'remover': 'remove',
       'iterator': '__iter__', }

class InstrumentedDict(dict):
    """An instrumented version of the built-in dict."""

    __instrumentation__ = {
        'iterator': 'itervalues', }

__canned_instrumentation = {
    list: InstrumentedList,
    Set: InstrumentedSet,
    dict: InstrumentedDict,
    }

__interfaces = {
    list: { 'appender': 'append',
            'remover':  'remove',
            'iterator': '__iter__',
            '_decorators': _list_decorators(), },
    Set: { 'appender': 'add',
           'remover': 'remove',
           'iterator': '__iter__',
           '_decorators': _set_decorators(), },
    # decorators are required for dicts and object collections.
    dict: { 'iterator': 'itervalues',
            '_decorators': _dict_decorators(), },
    # < 0.4 compatible naming, deprecated- use decorators instead.
    None: { }
    }


class MappedCollection(dict):
    """A basic dictionary-based collection class.

    Extends dict with the minimal bag semantics that collection classes require.
    ``set`` and ``remove`` are implemented in terms of a keying function: any
    callable that takes an object and returns an object for use as a dictionary
    key.
    """

    def __init__(self, keyfunc):
        """Create a new collection with keying provided by keyfunc.

        keyfunc may be any callable any callable that takes an object and
        returns an object for use as a dictionary key.

        The keyfunc will be called every time the ORM needs to add a member by
        value-only (such as when loading instances from the database) or remove
        a member.  The usual cautions about dictionary keying apply-
        ``keyfunc(object)`` should return the same output for the life of the
        collection.  Keying based on mutable properties can result in
        unreachable instances "lost" in the collection.
        """
        self.keyfunc = keyfunc

    def set(self, value, _sa_initiator=None):
        """Add an item to the collection, with a key provided by this instance's keyfunc."""

        key = self.keyfunc(value)
        self.__setitem__(key, value, _sa_initiator)
    set = collection.internally_instrumented(set)
    set = collection.appender(set)

    def remove(self, value, _sa_initiator=None):
        """Remove an item from the collection by value, consulting this instance's keyfunc for the key."""

        key = self.keyfunc(value)
        # Let self[key] raise if key is not in this collection
        if self[key] != value:
            raise exceptions.InvalidRequestError(
                "Can not remove '%s': collection holds '%s' for key '%s'. "
                "Possible cause: is the MappedCollection key function "
                "based on mutable properties or properties that only obtain "
                "values after flush?" %
                (value, self[key], key))
        self.__delitem__(key, _sa_initiator)
    remove = collection.internally_instrumented(remove)
    remove = collection.remover(remove)

    def _convert(self, dictlike):
        """Validate and convert a dict-like object into values for set()ing.

        This is called behind the scenes when a MappedCollection is replaced
        entirely by another collection, as in::

          myobj.mappedcollection = {'a':obj1, 'b': obj2} # ...

        Raises a TypeError if the key in any (key, value) pair in the dictlike
        object does not match the key that this collection's keyfunc would
        have assigned for that value.
        """

        for incoming_key, value in sautil.dictlike_iteritems(dictlike):
            new_key = self.keyfunc(value)
            if incoming_key != new_key:
                raise TypeError(
                    "Found incompatible key %r for value %r; this collection's "
                    "keying function requires a key of %r for this value." % (
                    incoming_key, value, new_key))
            yield value
    _convert = collection.converter(_convert)