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POSqlalchemy: avoiding multiple inheritance and having abstract base class
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copied!<p>So I have a bunch of tables using SQLAlchemy that are modelled as objects which inherit from the result to a call to <code>declarative_base()</code>. Ie:</p> <pre><code>Base = declarative_base() class Table1(Base): # __tablename__ & such here class Table2(Base): # __tablename__ & such here </code></pre> <p>Etc. I then wanted to have some common functionality available to each of my DB table classes, <a href="http://docs.sqlalchemy.org/en/latest/orm/extensions/declarative.html#declarative-mixins" rel="noreferrer">the easiest way to do this according to the docs</a> is to just do multiple inheritance:</p> <pre><code>Base = declarative_base() class CommonRoutines(object): @classmethod def somecommonaction(cls): # body here class Table1(CommonRoutines, Base): # __tablename__ & such here class Table2(CommonRoutines, Base): # __tablename__ & such here </code></pre> <p>The thing I don't like about this is A) multiple inheritance in general is a bit icky (gets tricky resolving things like <code>super()</code> calls, etc), B) if I add a new table I have to remember to inherit from both <code>Base</code> and <code>CommonRoutines</code>, and C) really that "CommonRoutines" class "is-a" type of table in a sense. Really what <code>CommonBase</code> is is an abstract base class which defines a set of fields & routines which are common to all tables. Put another way: "its-a" abstract table.</p> <p>So, what I'd like is this:</p> <pre><code>Base = declarative_base() class AbstractTable(Base): __metaclass__ = ABCMeta # make into abstract base class # define common attributes for all tables here, like maybe: id = Column(Integer, primary_key=True) @classmethod def somecommonaction(cls): # body here class Table1(AbstractTable): # __tablename__ & Table1 specific fields here class Table2(AbstractTable): # __tablename__ & Table2 specific fields here </code></pre> <p>But this of course doesn't work, as I then have to A) define a <code>__tablename__</code> for <code>AbstractTable</code>, B) the ABC aspect of things causes all sorts of headaches, and C) have to indicate some sort of DB relationship between <code>AbstractTable</code> and each individual table. </p> <p>So my question: is it possible to achieve this in a reasonable way? Ideally I'd like to enforce:</p> <ul> <li>No multiple inheritance</li> <li><code>CommonBase</code>/<code>AbstractTable</code> be abstract (ie cannot be instantiated)</li> </ul>

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