mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-15 05:07:16 -04:00
Mike Bayer
1e278de4cc
Applied on top of a pure run of black -l 79 in I7eda77fed3d8e73df84b3651fd6cfcfe858d4dc9, this set of changes resolves all remaining flake8 conditions for those codes we have enabled in setup.cfg. Included are resolutions for all remaining flake8 issues including shadowed builtins, long lines, import order, unused imports, duplicate imports, and docstring issues. Change-Id: I4f72d3ba1380dd601610ff80b8fb06a2aff8b0fe
114 lines
3.3 KiB
Python
114 lines
3.3 KiB
Python
"""Illustrate a many-to-many relationship between an
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"Order" and a collection of "Item" objects, associating a purchase price
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with each via an association object called "OrderItem"
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The association object pattern is a form of many-to-many which
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associates additional data with each association between parent/child.
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The example illustrates an "order", referencing a collection
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of "items", with a particular price paid associated with each "item".
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"""
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from datetime import datetime
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from sqlalchemy import and_
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from sqlalchemy import Column
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from sqlalchemy import create_engine
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from sqlalchemy import DateTime
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from sqlalchemy import Float
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from sqlalchemy import ForeignKey
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from sqlalchemy import Integer
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from sqlalchemy import String
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from sqlalchemy.ext.declarative import declarative_base
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from sqlalchemy.orm import relationship
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from sqlalchemy.orm import Session
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Base = declarative_base()
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class Order(Base):
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__tablename__ = "order"
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order_id = Column(Integer, primary_key=True)
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customer_name = Column(String(30), nullable=False)
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order_date = Column(DateTime, nullable=False, default=datetime.now())
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order_items = relationship(
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"OrderItem", cascade="all, delete-orphan", backref="order"
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)
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def __init__(self, customer_name):
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self.customer_name = customer_name
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class Item(Base):
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__tablename__ = "item"
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item_id = Column(Integer, primary_key=True)
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description = Column(String(30), nullable=False)
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price = Column(Float, nullable=False)
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def __init__(self, description, price):
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self.description = description
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self.price = price
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def __repr__(self):
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return "Item(%r, %r)" % (self.description, self.price)
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class OrderItem(Base):
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__tablename__ = "orderitem"
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order_id = Column(Integer, ForeignKey("order.order_id"), primary_key=True)
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item_id = Column(Integer, ForeignKey("item.item_id"), primary_key=True)
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price = Column(Float, nullable=False)
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def __init__(self, item, price=None):
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self.item = item
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self.price = price or item.price
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item = relationship(Item, lazy="joined")
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if __name__ == "__main__":
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engine = create_engine("sqlite://")
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Base.metadata.create_all(engine)
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session = Session(engine)
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# create catalog
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tshirt, mug, hat, crowbar = (
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Item("SA T-Shirt", 10.99),
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Item("SA Mug", 6.50),
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Item("SA Hat", 8.99),
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Item("MySQL Crowbar", 16.99),
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)
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session.add_all([tshirt, mug, hat, crowbar])
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session.commit()
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# create an order
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order = Order("john smith")
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# add three OrderItem associations to the Order and save
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order.order_items.append(OrderItem(mug))
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order.order_items.append(OrderItem(crowbar, 10.99))
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order.order_items.append(OrderItem(hat))
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session.add(order)
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session.commit()
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# query the order, print items
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order = session.query(Order).filter_by(customer_name="john smith").one()
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print(
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[
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(order_item.item.description, order_item.price)
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for order_item in order.order_items
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]
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)
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# print customers who bought 'MySQL Crowbar' on sale
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q = session.query(Order).join("order_items", "item")
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q = q.filter(
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and_(Item.description == "MySQL Crowbar", Item.price > OrderItem.price)
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)
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print([order.customer_name for order in q])
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