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sqla_yaml_fixtures

Load YAML data fixtures for SQLAlchemy

This package allows you to define some data in YAML and load them into a DB. The yaml data should correspond to SQLAlchemy declarative mappers.

Example:

- User:
  - __key__: joey
    username: joey
    email: [email protected]
    profile:
      name: Jeffrey

  - __key__: dee
    username: deedee
    email: [email protected]

- Profile:
  - user: dee
    name: Douglas

- Group:
  - name: Ramones
    members: [joey.profile, dee.profile]
  • The root of YAML contains a sequence of mapper names e.g. - User, - Profile etc
  • The order of these names should follow relationship dependencies
  • Every name should contain a sequence of instances
  • Each instance is a mapping of attribute -> value
  • the attributes are taken from the mapper __init__() (usually an attributes maps to a column)
  • The special field __key__ can be used to identify this instnace in a relationship reference e.g. The Profile.user
  • Note that any __key__ MUST be globally unique
  • In a to-one relationship the data can be directly nested in the parent data definition
  • References can access attributes using a dot notation, e.g. joey.profile
  • to-many relationships can be added as a list of references

The mapper definition for this example is in the test file.

Installation

pip install sqla-yaml-fixtures

API

This module expose a single function load(ModelBase, session, fixture_text, loader=None)

Where:

  • ModelBase is SQLAlchemy declarative base
  • session is SQLAlchemy session
  • fixture_text is a string containg the YAML fixtures
from sqlalchemy import create_engine
from sqlalchemy import Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import Session

import sqla_yaml_fixtures

BaseModel = declarative_base()

class User(BaseModel):
    __tablename__ = 'user'
    id = Column(Integer, primary_key=True)
    username = Column(String(150), nullable=False, unique=True)
    email = Column(String(254), unique=True)


def main():
    engine = create_engine('sqlite://')
    BaseModel.metadata.create_all(engine)
    connection = engine.connect()
    session = Session(bind=connection)

    fixture = """
    - User:
      - username: deedee
        email: [email protected]
      - username: joey
        email: [email protected]
    """
    sqla_yaml_fixtures.load(BaseModel, session, fixture)

    print('\n'.join(u.username for u in session.query(User).all()))

if __name__ == '__main__':
    main()

Note: the load() function performs a session.commit().

load() returns an instance of Store. Using this object get() method you can passing a key as argument you get a reference to the object added into the database. This is useful to easily get attributes that are generated by the database.

store = sqla_yaml_fixtures.load(BaseModel, session, fixture)
my_obj = store.get('dee')
print('Created object id: {}'.format(my_obj.id))

Warning

By default YAML is loaded using yaml.FullLoader, this is insecure when loading unstrusted input. It is possible to overwrite the loaded by setting loader param in the load() function.

Command Line

For basic usage there is also command line. Example:

$ python -m sqla_yaml_fixtures --db-url sqlite:///dev.db --db-base mypkg.models:Base --reset-db --alembic-stamp fixture.yaml

All available options:

$ python -m sqla_yaml_fixtures --help
usage: sqla_yaml_fixtures [-h] --db-base DB_BASE --db-url DB_URL [--yes]
                          [--reset-db] [--alembic-stamp] [--jinja2]
                          FILE [FILE ...]

load fixtures from yaml file into DB

positional arguments:
  FILE               YAML file with DB fixtures

optional arguments:
  -h, --help         show this help message and exit
  --db-base DB_BASE  SQLAlchemy Base class with schema metadata in the format
                     my_package.my_module:MyClass
  --db-url DB_URL    Database URL in the format
                     dialect+driver://username:password@host:port/database
  --yes              Do NOT ask for confirmation before applying fixtures
  --reset-db         Drop DB schema and data and re-create schema before
                     loading fixtures
  --alembic-stamp    Perform `alembic stamp head`
  --jinja2           load fixture files as jinja2 templates