Python marshmallow.fields 模块，Number() 实例源码

def inline(self, field, context):
        # type: (fields.Field, JitContext) -> Optional[str]
        """Generates a template for inlining string serialization.

        For example, generates "float(value) if value is not None else None"
        to serialize a float.  If `field.as_string` is `True` the result will
        be coerced to a string if not None.
        """
        if (is_overridden(field._validated, fields.Number._validated) or
                is_overridden(field._serialize, fields.Number._serialize)):
            return None
        result = field.num_type.__name__ + '({0})'
        if field.as_string and context.is_serializing:
            result = 'str({0})'.format(result)
        if field.allow_none is True:
            # Only emit the Null checking code if nulls are allowed.  If they
            # aren't allowed casting `None` to an integer will throw and the
            # slow path will take over.
            result += ' if {0} is not None else None'
        return result

def field_to_dynamo_type(field):
        """Given a marshmallow field object return the appropriate Dynamo type character"""
        if isinstance(field, fields.Raw):
            return 'B'
        if isinstance(field, fields.Number):
            return 'N'
        return 'S'