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Specific types behavior

Structures

Out of the box dataclass factory supports three types of structures:

  • dataclasses
  • TypedDict (total is also checked)
  • other classes with annotated __init__
Feature dataclass TypedDict Class with __init__
Parsing x x x
Name conversion x x x
Omit default x
Skip internal x x
Serializing x x x

Custom parsers and serializers

Not all types are supported out of the box. For example, it is unclear how to parse datetime: it can be represented as unixtime or iso format or something else. If you meet unsupported type you can provide your own parser and serializer:

examples/custom.py

Common schemas

We have subpackage called dataclass_factory.schema_helpers with some common schemas:

  • unixtime_schema - converts datetime to unixtime and vice versa
  • isotime_schema - converts datetime to string containing ISO 8601. Supported only on Python 3.7+
  • uuid_schema - converts UUID objects to string

Self referenced types

Just place correct annotations and use factory.

examples/self_referenced.py

Generic classes

Generic classes supported out of the box. The difference is that if no schema found for concrete class, it will be taken for generic.

examples/generic.py

Note

Always pass concrete type as as second argument of dump method. Otherwise it will be treated as generic due to type erasure.

Polymorphic parsing

Very common case is to select class based on information in data.

If required fields differ between classes, no configuration required. But sometimes you want to make a selection more explicitly. For example, if data field "type" equals to "item" data should be parsed as Item, if it is "group" then Group class should be used.

For such case you can use type_checker from schema_helpers module. It creates a function, which should be used on pre_parse step. By default it checks type field of data, but you can change it

examples/polymorphic.py

If you need you own pre_parse function, you can set it as parameter for type_checker factory.

For more complex cases you can write your own function. Just raise ValueError if you detected that current class is not acceptable for provided data, and parser will go to the next one in Union