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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 sqlautocode
_, 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/
PEP 8
_ compliant code.. _PEP 8: http://www.python.org/dev/peps/pep-0008/
To install, do::
pip install sqlacodegen
To include support for the PostgreSQL CITEXT
extension type (which should be
considered as tested only under a few environments) specify the citext
extra::
pip install sqlacodegen[citext]
To include support for the PostgreSQL GEOMETRY
, GEOGRAPHY
, and RASTER
types
(which should be considered as tested only under a few environments) specify the
geoalchemy2
extra:
To include support for the PostgreSQL PGVECTOR
extension type, specify the
pgvector
extra::
pip install sqlacodegen[pgvector]
.. code-block:: bash
pip install sqlacodegen[geoalchemy2]
At the minimum, you have to give sqlacodegen a database URL. The URL is passed directly
to SQLAlchemy's create_engine()
method so please refer to
SQLAlchemy's documentation
for instructions on how to construct a proper URL.
Examples::
sqlacodegen postgresql:///some_local_db
sqlacodegen --generator tables mysql+pymysql://user:password@localhost/dbname
sqlacodegen --generator dataclasses sqlite:///database.db
To see the list of generic options::
sqlacodegen --help
.. _create_engine(): http://docs.sqlalchemy.org/en/latest/core/engines.html#sqlalchemy.create_engine .. _SQLAlchemy's documentation: http://docs.sqlalchemy.org/en/latest/core/engines.html
The selection of a generator determines the
The following built-in generators are available:
tables
(only generates Table
objects, for those who don't want to use the ORM)declarative
(the default; generates classes inheriting from declarative_base()
dataclasses
(generates dataclass-based models; v1.4+ only)sqlmodels
(generates model classes for SQLModel_).. _SQLModel: https://sqlmodel.tiangolo.com/
The following options can be turned on by passing them using --options
(multiple
values must be delimited by commas, e.g. --options noconstraints,nobidi
):
tables
noconstraints
: ignore constraints (foreign key, unique etc.)nocomments
: ignore table/column commentsnoindexes
: ignore indexesdeclarative
tables
use_inflect
: use the inflect
library when naming classes and relationships
(turning plural names into singular; see below for details)nojoined
: don't try to detect joined-class inheritance (see below for details)nobidi
: generate relationships in a unidirectional fashion, so only the
many-to-one or first side of many-to-many relationships gets a relationship
attribute, as on v2.Xdataclasses
declarative
sqlmodel
declarative
The code generators that generate classes try to generate model classes whenever
possible. There are two circumstances in which a Table
is generated instead:
Model class naming logic ++++++++++++++++++++++++
By default, table names are converted to valid PEP 8 compliant class names by replacing
all characters unsuitable for Python identifiers with _
. Then, each valid parts
(separated by underscores) are title cased and then joined together, eliminating the
underscores. So, example_name
becomes ExampleName
.
If the use_inflect
option is used, the table name (which is assumed to be in
English) is converted to singular form using the "inflect" library. For example,
sales_invoices
becomes SalesInvoice
. Since table names are not always in
English, and the inflection process is far from perfect, inflection is disabled by
default.
Relationship detection logic ++++++++++++++++++++++++++++
Relationships are detected based on existing foreign key constraints as follows:
sqlmodel
generator) an association table
is found to exist between two tablesA table is considered an association table if it satisfies all of the following conditions:
Relationship naming logic +++++++++++++++++++++++++
Relationships are typically named based on the table name of the opposite class.
For example, if a class has a relationship to another class with the table named
companies
, the relationship would be named companies
(unless the use_inflect
option was enabled, in which case it would be named company
in the case of a
many-to-one or one-to-one relationship).
A special case for single column many-to-one and one-to-one relationships, however, is
if the column is named like employer_id
. Then the relationship is named employer
due to that _id
suffix.
For self referential relationships, the reverse side of the relationship will be named
with the _reverse
suffix appended to it.
If the built-in generators with all their options don't quite do what you want, you can
customize the logic by subclassing one of the existing code generator classes. Override
whichever methods you need, and then add an entry point
_ in the
sqlacodegen.generators
namespace that points to your new class. Once the entry point
is in place (you typically have to install the project with pip install
), you can
use --generator <yourentrypoint>
to invoke your custom code generator.
For examples, you can look at sqlacodegen's own entry points in its pyproject.toml
_.
.. _entry point: https://setuptools.readthedocs.io/en/latest/userguide/entry_point.html .. _pyproject.toml: https://github.com/agronholm/sqlacodegen/blob/master/pyproject.toml
If you have problems or other questions, you should start a discussion on the
sqlacodegen discussion forum
. As an alternative, you could also try your luck on the
sqlalchemy room on Gitter.
.. _sqlacodegen discussion forum: https://github.com/agronholm/sqlacodegen/discussions/categories/q-a .. _sqlalchemy: https://app.gitter.im/#/room/#sqlalchemy_community:gitter.im