Pydantic change detection

Installation

Just use pip install pydantic-changedetect to install the library.

About

When working with database models it is pretty common to want to detect changes to the model attributes. The ChangeDetectionMixin just provides this mechanism to any pydantic models. Changes will be detected and stored after the model was constructed.

Using the ChangeDetectionMixin the pydantic models are extended, so:

• obj.__changed_fields__ contains a list of all changed fields
  • obj.__self_changed_fields__ contains a list of all changed fields for the current object, ignoring all nested models.
  • obj.__changed_fields_recursive__ contains a list of all changed fields and also include the named of the fields changed in nested models using a dotted field name syntax (like nested.field).
• obj.__original__ will include the original values of all changed fields in a dict.
• obj.has_changed() returns True if any field has changed.
• obj.set_changed() manually sets fields as changed.
  • obj.set_changed("field_a", "field_b") will set multiple fields as changed.
  • obj.set_changed("field_a", original="old") will set a single field as changed and also store its original value.
• obj.reset_changed() resets all changed fields.
• obj.dict() and obj.json() accept an additional parameter exclude_unchanged, which - when set to True - will only export the changed fields

Example

import pydantic
from pydantic_changedetect import ChangeDetectionMixin

class Something(ChangeDetectionMixin, pydantic.BaseModel):
    name: str


something = Something(name="something")
something.has_changed  # = False
something.__changed_fields__  # = set()
something.name = "something else"
something.has_changed  # = True
something.__changed_fields__  # = {"name"}

Restrictions

ChangeDetectionMixin currently cannot detect changes inside lists, dicts and other structured objects. In those cases you are required to set the changed state yourself using set_changed(). It is recommended to pass the original value to set_changed() when you want to also keep track of the actual changes compared to the original value. Be advised to .copy() the original value as lists/dicts will always be changed in place.

Contributing

If you want to contribute to this project, feel free to just fork the project, create a dev branch in your fork and then create a pull request (PR). If you are unsure about whether your changes really suit the project please create an issue first, to talk about this.