catalyst

Catalyst is an lightweight library for converting complex datatypes to and from native Python datatypes.

from datetime import datetime
from pprint import pprint

from catalyst import Catalyst, String, Datetime, NestField


class Writer:
    def __init__(self, name):
        self.name = name


class Article:
    def __init__(self, title, content, pub_date, author):
        self.title = title
        self.content = content
        self.pub_date = pub_date
        self.author = author


class WriterCatalyst(Catalyst):
    name = String(min_length=0, max_length=12)

writerCatalyst = WriterCatalyst()


class ArticleCatalyst(Catalyst):
    title = String(min_length=1, max_length=48)
    content = String(min_length=1, max_length=500)
    pub_date = Datetime('%Y/%m/%d %H:%M:%S')
    author = NestField(writerCatalyst)

articleCatalyst = ArticleCatalyst()


fossen = Writer('fossen')
article = Article('Test', 'content', datetime(2019, 1, 1), fossen)


# Convert object to formatted data
dump_result = articleCatalyst.dump(article)
pprint(dump_result)
# {'author': {'name': 'fossen'},
#  'content': 'content',
#  'pub_date': '2019/01/01 00:00:00',
#  'title': 'Test'}


# Validate and convert raw data to valid data
load_result = articleCatalyst.load(dump_result)

pprint(type(load_result))
# <class 'catalyst.catalyst.LoadDict'>
pprint(load_result)
# {'author': LoadResult(is_valid=True, valid_data={'name': 'fossen'}),
#  'content': 'content',
#  'pub_date': datetime.datetime(2019, 1, 1, 0, 0),
#  'title': 'Test'}


# Distinguish invalid data from raw data
invalid_data = {'title': 'Test', 'pub_date': '2019/01/01', 'author': {}}

load_result = articleCatalyst.load(invalid_data)
pprint(load_result.is_valid)
# False
pprint(load_result.valid_data)
# {'title': 'Test'}
pprint(load_result.invalid_data)
# {'author': {}, 'pub_date': '2019/01/01'}
pprint(load_result.errors)
# {'author': ValidationError(LoadResult(is_valid=False, errors={'name': 'Field may not be None.'})),
#  'content': ValidationError('Field may not be None.'),
#  'pub_date': ValueError("time data '2019/01/01' does not match format '%Y/%m/%d %H:%M:%S'")}

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Catalyst is inspired by marshmallow.