Pythonic way to check if a dataclass field has a default value

问题

I've been using python 3.7 lately and was looking for ways to leverage the new dataclasses. Basically I had a method that iterates over the dataclass fields and checks if they have a default value:

from dataclasses import fields, MISSING

@classmethod
def from_json(cls)
    datacls_fields = fields(cls)
    for field in datacls_fields:
        if  (field.default != MISSING):
            #...

However in the official documentation, it says:

MISSING value is a sentinel object used to detect if the default and default_factory parameters are provided. This sentinel is used because None is a valid value for default. No code should directly use the MISSING value.

Anyone knows a better/more pythonic way to do it?

来源：https://stackoverflow.com/questions/53589794/pythonic-way-to-check-if-a-dataclass-field-has-a-default-value