mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-13 20:27:35 -04:00
Mike Bayer
40f8aadd58
- added READMEs to all examples in each __init__.py and added to sphinx documentation - added versioning example - removed vertical/vertical.py, the dictlikes are more straightforward
87 lines
2.1 KiB
Python
87 lines
2.1 KiB
Python
"""a directed graph example."""
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from sqlalchemy import MetaData, Table, Column, Integer, ForeignKey
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from sqlalchemy.orm import mapper, relation, create_session
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import logging
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logging.basicConfig()
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logging.getLogger('sqlalchemy.engine').setLevel(logging.INFO)
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meta = MetaData('sqlite://')
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nodes = Table('nodes', meta,
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Column("nodeid", Integer, primary_key=True)
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)
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# here we have lower.nodeid <= higher.nodeid
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edges = Table('edges', meta,
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Column("lower_id", Integer, ForeignKey('nodes.nodeid'), primary_key=True),
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Column("higher_id", Integer, ForeignKey('nodes.nodeid'), primary_key=True)
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)
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meta.create_all()
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class Node(object):
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def __init__(self, id):
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self.nodeid = id
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def add_neighbor(self, othernode):
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Edge(self, othernode)
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def higher_neighbors(self):
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return [x.higher_node for x in self.lower_edges]
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def lower_neighbors(self):
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return [x.lower_node for x in self.higher_edges]
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class Edge(object):
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def __init__(self, n1, n2):
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if n1.nodeid < n2.nodeid:
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self.lower_node = n1
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self.higher_node = n2
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else:
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self.lower_node = n2
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self.higher_node = n1
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mapper(Node, nodes)
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mapper(Edge, edges, properties={
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'lower_node':relation(Node,
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primaryjoin=edges.c.lower_id==nodes.c.nodeid, backref='lower_edges'),
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'higher_node':relation(Node,
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primaryjoin=edges.c.higher_id==nodes.c.nodeid, backref='higher_edges')
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}
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)
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session = create_session()
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# create a directed graph like this:
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# n1 -> n2 -> n5
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# -> n7
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# -> n3 -> n6
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n1 = Node(1)
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n2 = Node(2)
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n3 = Node(3)
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n4 = Node(4)
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n5 = Node(5)
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n6 = Node(6)
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n7 = Node(7)
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n2.add_neighbor(n5)
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n3.add_neighbor(n6)
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n7.add_neighbor(n2)
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n1.add_neighbor(n3)
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n2.add_neighbor(n1)
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[session.add(x) for x in [n1, n2, n3, n4, n5, n6, n7]]
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session.flush()
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session.expunge_all()
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n2 = session.query(Node).get(2)
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n3 = session.query(Node).get(3)
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assert [x.nodeid for x in n3.higher_neighbors()] == [6]
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assert [x.nodeid for x in n3.lower_neighbors()] == [1]
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assert [x.nodeid for x in n2.lower_neighbors()] == [1]
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assert [x.nodeid for x in n2.higher_neighbors()] == [5,7]
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