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2012-11-22T00:19:38.920
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<p>Out of my head:</p> <p>I define two example domains, <code>User</code> and <code>Animal</code>, an base storage class <code>Store</code> and two specialized Storage classes <code>UserStore</code> and <code>AnimalStore</code>. Use of context manager closes db connection (for simplicity I use sqlite in this example):</p> <pre><code>import sqlite3 def get_connection(): return sqlite3.connect('test.sqlite') class StoreException(Exception): def __init__(self, message, *errors): Exception.__init__(self, message) self.errors = errors # domains class User(): def __init__(self, name): self.name = name class Animal(): def __init__(self, name): self.name = name # base store class class Store(): def __init__(self): try: self.conn = get_connection() except Exception as e: raise StoreException(*e.args, **e.kwargs) self._complete = False def __enter__(self): return self def __exit__(self, type_, value, traceback): # can test for type and handle different situations self.close() def complete(self): self._complete = True def close(self): if self.conn: try: if self._complete: self.conn.commit() else: self.conn.rollback() except Exception as e: raise StoreException(*e.args) finally: try: self.conn.close() except Exception as e: raise StoreException(*e.args) # store for User obects class UserStore(Store): def add_user(self, user): try: c = self.conn.cursor() # this needs an appropriate table c.execute('INSERT INTO user (name) VALUES(?)', (user.name,)) except Exception as e: raise StoreException('error storing user') # store for Animal obects class AnimalStore(Store): def add_animal(self, animal): try: c = self.conn.cursor() # this needs an appropriate table c.execute('INSERT INTO animal (name) VALUES(?)', (animal.name,)) except Exception as e: raise StoreException('error storing animal') # do something try: with UserStore() as user_store: user_store.add_user(User('John')) user_store.complete() with AnimalStore() as animal_store: animal_store.add_animal(Animal('Dog')) animal_store.add_animal(Animal('Pig')) animal_store.add_animal(Animal('Cat')) animal_store.add_animal(Animal('Wolf')) animal_store.complete() except StoreException as e: # exception handling here print(e) </code></pre>
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1. POImplementation of Repository Pattern in Python?
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1. COYes, this does implement the Repository Pattern. In a library providing it, I would hope for each storage backend to provide a default strategy to map models to storage, so no hand-written SQL is required.
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2. CO@graham [SQLAlchemy](http://www.sqlalchemy.org/) might be what you want, but it's not lightweight, see [SQLAlchemy session](http://docs.sqlalchemy.org/en/latest/orm/session.html).
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