Convert features in an Esri GDB feature class to an Esri JSON-style list of features, represented as a list of feature dictionaries.

convert_feature_class_to_features_list.py

def convert_feature_class_to_features_list(source_feature_class):
    # convert feature class features to Esri features list
    # (JSON represented as a list of feature dictionaries)

    # ignore 'Geometry' field type and manually ask for JSON-formatted geometry with 'SHAPE@JSON' below
    # you could also add the 'OID' field type to ignore if you need to add these features to a hosted feature service
    field_types_to_ignore = ['Geometry']

    # establish the out fields, minus any fields that need to be ignored
    out_fields = [
        i.name for i
        in arcpy.Describe(source_feature_class).fields
        if i.type not in field_types_to_ignore
    ]
    # and specifically ask for geometry info in JSON format
    out_fields.append('SHAPE@JSON')

    features = [
        {
            'attributes': {
                out_fields[attribute_index]: attribute_value
                for attribute_index, attribute_value
                in enumerate(row[:-1])
            },
            'geometry': json.loads(row[-1])
        } for row in arcpy.da.SearchCursor(
            in_table=source_feature_class,
            field_names=out_fields
        )
    ]

    return features