ValidatedDC

Dataclass with data validation. Checks the value of its fields by their annotations.

Capabilities

ValidatedDC is a regular Python dataclass.

1. Support for standard types and custom Python classes.
2. Support for some aliases from the typing module, namely: Any, List, Literal, Optional, Union. These aliases can be embedded in each other.
3. When initializing an instance of a class, you can use the value of the field dict instead of the ValidatedDC instance specified in the field annotation (useful, for example, when retrieving data via api).
4. Data validation occurs immediately after an instance is created, and can also be run by the is_valid() function at any time.
5. The get_errors() function will show the full traceback of errors in the fields, including errors of nested classes.

See detailed in the examples folder.

Installation

pip install validated-dc

Python versions support

Versions 3.7, 3.8 and 3.9 are currently supported.

To work with version python 3.7 you need to install:

pip install typing_extensions

Quick example

from dataclasses import dataclass
from typing import List, Union

from validated_dc import ValidatedDC, get_errors, is_valid


# Some combinations of List and Union

@dataclass
class Foo(ValidatedDC):
    value: Union[int, List[int]]


@dataclass
class Bar(ValidatedDC):
    foo: Union[Foo, List[Foo]]


# --- Valid input ---

foo = {'value': 1}
instance = Bar(foo=foo)
assert get_errors(instance) is None
assert instance == Bar(foo=Foo(value=1))

foo = {'value': [1, 2]}
instance = Bar(foo=foo)
assert get_errors(instance) is None
assert instance == Bar(foo=Foo(value=[1, 2]))

foo = [{'value': 1}, {'value': 2}]
instance = Bar(foo=foo)
assert get_errors(instance) is None
assert instance == Bar(foo=[Foo(value=1), Foo(value=2)])

foo = [{'value': [1, 2]}, {'value': [3, 4]}]
instance = Bar(foo=foo)
assert get_errors(instance) is None
assert instance == Bar(foo=[Foo(value=[1, 2]), Foo(value=[3, 4])])


# --- Invalid input ---

foo = {'value': 'S'}
instance = Bar(foo=foo)
assert get_errors(instance)
assert instance == Bar(foo={'value': 'S'})
# fix
instance.foo['value'] = 1
assert is_valid(instance)
assert get_errors(instance) is None
assert instance == Bar(foo=Foo(value=1))

foo = [{'value': [1, 2]}, {'value': ['S', 4]}]
instance = Bar(foo=foo)
assert get_errors(instance)
assert instance == Bar(foo=[{'value': [1, 2]}, {'value': ['S', 4]}])
# fix
instance.foo[1]['value'][0] = 3
assert is_valid(instance)
assert get_errors(instance) is None
assert instance == Bar(foo=[Foo(value=[1, 2]), Foo(value=[3, 4])])


# --- get_errors() ---

foo = {'value': 'S'}
instance = Bar(foo=foo)
print(get_errors(instance))
# {
#   'foo': [
#       # An unsuccessful attempt to use the dictionary to create a Foo instance
#       InstanceValidationError(
#           value_repr="{'value': 'S'}",
#           value_type=<class 'dict'>,
#           annotation=<class '__main__.Foo'>,
#           exception=None,
#           errors={
#               'value': [
#                   BasicValidationError(  # because the str isn't an int
#                       value_repr='S', value_type=<class 'str'>,
#                       annotation=<class 'int'>, exception=None
#                   ),
#                   BasicValidationError(  # and the str is not a list of int
#                       value_repr='S', value_type=<class 'str'>,
#                       annotation=typing.List[int], exception=None
#                   )
#               ]
#           }
#       ),
#       BasicValidationError(  # the dict is not a list of Foo
#           value_repr="{'value': 'S'}",
#           value_type=<class 'dict'>,
#           annotation=typing.List[__main__.Foo],
#           exception=None
#       )
#   ]
# }