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Diffstat (limited to 'examples/derived_attributes/attributes.py')
| -rw-r--r-- | examples/derived_attributes/attributes.py | 168 |
1 files changed, 0 insertions, 168 deletions
diff --git a/examples/derived_attributes/attributes.py b/examples/derived_attributes/attributes.py deleted file mode 100644 index f36cbd541..000000000 --- a/examples/derived_attributes/attributes.py +++ /dev/null @@ -1,168 +0,0 @@ -from functools import update_wrapper -import new - -class method(object): - def __init__(self, func, expr=None): - self.func = func - self.expr = expr or func - - def __get__(self, instance, owner): - if instance is None: - return new.instancemethod(self.expr, owner, owner.__class__) - else: - return new.instancemethod(self.func, instance, owner) - - def expression(self, expr): - self.expr = expr - return self - -class property_(object): - def __init__(self, fget, fset=None, fdel=None, expr=None): - self.fget = fget - self.fset = fset - self.fdel = fdel - self.expr = expr or fget - update_wrapper(self, fget) - - def __get__(self, instance, owner): - if instance is None: - return self.expr(owner) - else: - return self.fget(instance) - - def __set__(self, instance, value): - self.fset(instance, value) - - def __delete__(self, instance): - self.fdel(instance) - - def setter(self, fset): - self.fset = fset - return self - - def deleter(self, fdel): - self.fdel = fdel - return self - - def expression(self, expr): - self.expr = expr - return self - -### Example code - -from sqlalchemy import Table, Column, Integer, create_engine, func -from sqlalchemy.orm import sessionmaker, aliased -from sqlalchemy.ext.declarative import declarative_base - -Base = declarative_base() - -class BaseInterval(object): - @method - def contains(self,point): - """Return true if the interval contains the given interval.""" - - return (self.start <= point) & (point < self.end) - - @method - def intersects(self, other): - """Return true if the interval intersects the given interval.""" - - return (self.start < other.end) & (self.end > other.start) - - @method - def _max(self, x, y): - """Return the max of two values.""" - - return max(x, y) - - @_max.expression - def _max(cls, x, y): - """Return the SQL max of two values.""" - - return func.max(x, y) - - @method - def max_length(self, other): - """Return the longer length of this interval and another.""" - - return self._max(self.length, other.length) - - def __repr__(self): - return "%s(%s..%s)" % (self.__class__.__name__, self.start, self.end) - -class Interval1(BaseInterval, Base): - """Interval stored as endpoints""" - - __table__ = Table('interval1', Base.metadata, - Column('id', Integer, primary_key=True), - Column('start', Integer, nullable=False), - Column('end', Integer, nullable=False) - ) - - def __init__(self, start, end): - self.start = start - self.end = end - - @property_ - def length(self): - return self.end - self.start - -class Interval2(BaseInterval, Base): - """Interval stored as start and length""" - - __table__ = Table('interval2', Base.metadata, - Column('id', Integer, primary_key=True), - Column('start', Integer, nullable=False), - Column('length', Integer, nullable=False) - ) - - def __init__(self, start, length): - self.start = start - self.length = length - - @property_ - def end(self): - return self.start + self.length - - - -engine = create_engine('sqlite://', echo=True) - -Base.metadata.create_all(engine) - -session = sessionmaker(engine)() - -intervals = [Interval1(1,4), Interval1(3,15), Interval1(11,16)] - -for interval in intervals: - session.add(interval) - session.add(Interval2(interval.start, interval.length)) - -session.commit() - -for Interval in (Interval1, Interval2): - print "Querying using interval class %s" % Interval.__name__ - - print - print '-- length less than 10' - print [(i, i.length) for i in - session.query(Interval).filter(Interval.length < 10).all()] - - print - print '-- contains 12' - print session.query(Interval).filter(Interval.contains(12)).all() - - print - print '-- intersects 2..10' - other = Interval1(2,10) - result = session.query(Interval).\ - filter(Interval.intersects(other)).\ - order_by(Interval.length).all() - print [(interval, interval.intersects(other)) for interval in result] - - print - print '-- longer length' - interval_alias = aliased(Interval) - print session.query(Interval.length, - interval_alias.length, - Interval.max_length(interval_alias)).all() |