New functions and methods:

• pony.orm.serialization module with the to_dict() and to_json() functions was added. Before this release you could use the to_dict() method of an entity instance in order to get a key-value dictionary structure for a specific entity instance. Sometimes you might need to serialize not only the instance itself, but also the instance’s related objects. In this case you can use the to_dict() function from the pony.orm.serialization module.
  • to_dict() – receives an entity instance or a list of instances and returns a dictionary structure which keeps the passed object(s) and immediate related objects
  • to_json() – uses `to_dict()` and returns JSON representation of the to_dict() result
• Query.prefetch() – allows to specify which related objects or attributes should be loaded from the database along with the query result . Example:

        select(s for s in Student)\
            .prefetch(Group, Department, Student.courses)
  

• obj.flush() – allows flush a specific entity to the database
• obj.get_pk() – return the primary key value for an entity instance
• py_check parameter for attributes added. This parameter allows you to specify a function which will be used for checking the value before it is assigned to the attribute. The function should return True/False or can raise ValueError exception if the check failed. Example:

      class Student(db.Entity):
          name = Required(unicode)
          gpa = Required(float, py_check=lambda v: v >= 0 and v <= 5)
  

  New types:

  • time and timedelta – now you can use these types for attribute declaration. Also you can use timedelta and a combination of datetime + timedelta types inside queries.

  New hooks:

  • after_insert, after_update, after_delete - these hooks are called when an object was inserted, updated or deleted in the database respectively (link)
  • Added support for pymysql – pure Python MySQL client. Currently it is used as a fallback for MySQLdb interface

  Other changes and bug fixes

  • obj.order_by() method is deprecated, use Entity.select().order_by() instead
  • obj.describe() now displays composite primary keys
  • Fixes #50: PonyORM does not escape _ and % in LIKE queries
  • Fixes #51: Handling of one-to-one relations in declarative queries
  • Fixes #52: An attribute without a column should not have rbits & wbits
  • Fixes #53: Column generated at the wrong side of "one-to-one" relationship
  • Fixes #55: obj.to_dict() should do flush at first if the session cache is modified
  • Fixes #57: Error in to_dict() when to-one attribute value is None
  • Fixes #70: EntitySet allows to add and remove None
  • Check that the entity name starts with a capital letter and throw exception if it is not then raise the ERDiagramError: Entity class name should start with a capital letter exception