Serializer HooksΒΆ

Note: To customize the load or dump process for annotated types instead of individual fields, please see the Type Hooks section.

You can optionally add hooks that are run before a JSON string or a Python dict object is loaded to a dataclass instance, or before the dataclass instance is converted back to a Python dict object.

To customize the load process, simply implement the __post_init__ method which will be run by the dataclass decorator.

To customize the dump process, simply extend from DumpMixin and override the __pre_as_dict__ method which will be called whenever you invoke the to_dict or to_json methods. Please note that this will pass in the original dataclass instance, so updating any values will affect the fields of the underlying dataclass (this might change in a future revision).

A simple example to illustrate both approaches is shown below:

from dataclasses import dataclass
from dataclass_wizard import JSONSerializable, DumpMixin

class MyClass(JSONSerializable, DumpMixin):
    my_str: str
    my_int: int

    def __post_init__(self):
        self.my_str = self.my_str.title()

    def __pre_as_dict__(self):
        self.my_str = self.my_str.swapcase()

data = {"my_str": "my string", "myInt": "10"}

c = MyClass.from_dict(data)
# prints:
#   MyClass(my_str='My String', my_int=10)

string = c.to_json()
# prints:
#   {"myStr": "mY sTRING", "myInt": 10}