by agronholm

agronholm / sqlacodegen

Automatic model code generator for SQLAlchemy

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This is a tool that reads the structure of an existing database and generates the appropriate SQLAlchemy model code, using the declarative style if possible.

This tool was written as a replacement for

_, which was suffering from several issues (including, but not limited to, incompatibility with Python 3 and the latest SQLAlchemy version).

.. _sqlautocode: http://code.google.com/p/sqlautocode/


  • Supports SQLAlchemy 0.8.x - 1.3.x
  • Produces declarative code that almost looks like it was hand written
  • Produces
    PEP 8
    _ compliant code
  • Accurately determines relationships, including many-to-many, one-to-one
  • Automatically detects joined table inheritance
  • Excellent test coverage

.. _PEP 8: http://www.python.org/dev/peps/pep-0008/

Usage instructions


To install, do::

pip install sqlacodegen

Example usage

At the minimum, you have to give sqlacodegen a database URL. The URL is passed directly to SQLAlchemy's

_ method so please refer to
SQLAlchemy's documentation
_ for instructions on how to construct a proper URL.


sqlacodegen postgresql:///some_local_db
sqlacodegen mysql+oursql://user:[email protected]/dbname
sqlacodegen sqlite:///database.db

To see the full list of options::

sqlacodegen --help

.. createengine(): http://docs.sqlalchemy.org/en/latest/core/engines.html#sqlalchemy.create_engine .. _SQLAlchemy's documentation: http://docs.sqlalchemy.org/en/latest/core/engines.html

Why does it sometimes generate classes and sometimes Tables?

Unless the

option is used, sqlacodegen tries to generate declarative model classes from each table. There are two circumstances in which a
is generated instead:
  • the table has no primary key constraint (which is required by SQLAlchemy for every model class)
  • the table is an association table between two other tables (see below for the specifics)

Model class naming logic

The table name (which is assumed to be in English) is converted to singular form using the "inflect" library. Then, every underscore is removed while transforming the next letter to upper case. For example,


Relationship detection logic

Relationships are detected based on existing foreign key constraints as follows:

  • many-to-one: a foreign key constraint exists on the table
  • one-to-one: same as many-to-one, but a unique constraint exists on the column(s) involved
  • many-to-many: an association table is found to exist between two tables

A table is considered an association table if it satisfies all of the following conditions:

. has exactly two foreign key constraints

. all its columns are involved in said constraints

Relationship naming logic

Relationships are typically named based on the opposite class name. For example, if an

class has a column named
which has a foreign key to
, the relationship is named

A special case for single column many-to-one and one-to-one relationships, however, is if the column is named like

. Then the relationship is named
due to that

If more than one relationship would be created with the same name, the latter ones are appended numeric suffixes, starting from 1.

Getting help

If you have problems or other questions, you can either:

  • Ask on the
    SQLAlchemy Google group
    _, or
  • Ask on the
    channel on
    Freenode IRC

.. SQLAlchemy Google group: http://groups.google.com/group/sqlalchemy .. _Freenode IRC: http://freenode.net/ircservers.shtml

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