mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-28 03:26:01 -04:00
Mike Bayer
88 lines
2.4 KiB
Python
88 lines
2.4 KiB
Python
class ProxyDict(object):
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def __init__(self, parent, collection_name, childclass, keyname):
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self.parent = parent
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self.collection_name = collection_name
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self.childclass = childclass
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self.keyname = keyname
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@property
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def collection(self):
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return getattr(self.parent, self.collection_name)
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def keys(self):
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descriptor = getattr(self.childclass, self.keyname)
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return [x[0] for x in self.collection.values(descriptor)]
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def __getitem__(self, key):
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x = self.collection.filter_by(**{self.keyname:key}).first()
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if x:
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return x
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else:
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raise KeyError(key)
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def __setitem__(self, key, value):
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try:
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existing = self[key]
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self.collection.remove(existing)
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except KeyError:
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pass
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self.collection.append(value)
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from sqlalchemy.ext.declarative import declarative_base
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from sqlalchemy import create_engine, Column, Integer, String, ForeignKey
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from sqlalchemy.orm import sessionmaker, relationship
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engine=create_engine('sqlite://', echo=True)
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Base = declarative_base(engine)
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class Parent(Base):
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__tablename__ = 'parent'
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id = Column(Integer, primary_key=True)
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name = Column(String(50))
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_collection = relationship("Child", lazy="dynamic", cascade="all, delete-orphan")
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@property
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def child_map(self):
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return ProxyDict(self, '_collection', Child, 'key')
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class Child(Base):
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__tablename__ = 'child'
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id = Column(Integer, primary_key=True)
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key = Column(String(50))
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parent_id = Column(Integer, ForeignKey('parent.id'))
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def __repr__(self):
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return "Child(key=%r)" % self.key
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Base.metadata.create_all()
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sess = sessionmaker()()
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p1 = Parent(name='p1')
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sess.add(p1)
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print "\n---------begin setting nodes, autoflush occurs\n"
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p1.child_map['k1'] = Child(key='k1')
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p1.child_map['k2'] = Child(key='k2')
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# this will autoflush the current map.
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# ['k1', 'k2']
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print "\n---------print keys - flushes first\n"
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print p1.child_map.keys()
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# k1
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print "\n---------print 'k1' node\n"
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print p1.child_map['k1']
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print "\n---------update 'k2' node - must find existing, and replace\n"
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p1.child_map['k2'] = Child(key='k2')
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print "\n---------print 'k2' key - flushes first\n"
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# k2
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print p1.child_map['k2']
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print "\n---------print all child nodes\n"
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# [k1, k2b]
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print sess.query(Child).all()
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