Marsha

A serialization and validation library for python 3 based on the typing module.

Status

🔬 Experimental

Don't put this code on servers. You can, but you probably shouldn't.

Documentation

📖 https://deckar01.gitlab.io/marsha

Features

💂 Strictness

When using python's builtin types for schema annotations, the data must be instances of the specified types or the load operation will fail with an exception. Unexpected and missing data will error by default.

🕵 Clarity

Validation errors mirror the structure of the data, provide insight into the values that caused the error, and present meaningful information to help resolve the problem.

🏃 Speed

The default functionality is fast and lean. The performance degrades gracefully as complex functionality is explicitly opted into by the developer.

🤸 Flexibility

Custom data types are created by defining formatter classes, then transfored into types compatible with the builtin typing module.

💃 Expressiveness

Python's builtin typing generics can be leveraged to declare complex type unions that know how to automatically handle multiple types using a syntax that is explicit and concise.

Installation

pip install marsha

Usage

Need to create database model instances from user input and expose them in serialized form?

Creating a schema that is separate from the model is a useful way to declare a "view" and allows defining multiple schemas to control how data is exposed in different contexts.

from my_app.database_models import Artist, Album

import marsha
from typing import List

@marsha.schema(Artist)
class ArtistSchema:
    name: str

@marsha.schema(Album)
class AlbumSchema:
    title: str
    artists: List[Artist]

# dict -> Album
album = marsha.load(album_data, Album)
# Do stuff
album.save()
# Album -> dict
response_data = marsha.dump(album)

Just need to validate some data and convert it to the correct type?

You can automatically register the type annotations of any model as a schema by adding the schema decorator.

import marsha
from typing import List

@marsha.schema()
class Artist(dict):
    name: str

@marsha.schema()
class Album(dict):
    title: str
    artists: List[Artist]

# dict -> dict
album = marsha.load(album_data, Album)
# Do stuff
first_artist = album['artists'][0]

Development

📚 Dependencies

# python >= 3.6
pip install -r dev-requirements.txt

🏅 Testing

# Quick testing.
flake8
pytest
# Ensure all statements and branches are covered with tests.
pytest --cov=marsha --cov-branch --cov-report html --cov-report term
# Ensure documentations changes render correctly.
make html