Find field throwing error in Python Dataclass conversion

Question

I'm trying to convert a json array to a Python list of typed objects. It's data from Teltonika FOTA

The call result_list = fromlist(FotaDevice, intermediate_list) is failing with the error message TypeError: strptime() argument 1 must be str, not None

imports are:

from dataclasses import dataclass
from dataclass_wizard import fromlist, asdict, DateTimePattern, JSONWizard
from typing import Optional

The dataclass is as follows:

@dataclass
class FotaDevice(JSONWizard, debug=logging.DEBUG):
    imei:int
    serial:int
    model:str
    spec_id:int
    platform_id:int
    current_configuration:Optional[str]
    current_firmware:str
    description:Optional[str]
    company_id:int
    group_id:Optional[int]
    track:int
    first_login:Optional[DateTimePattern['%Y-%m-%d %H:%M:%S']]
    seen_at:Optional[DateTimePattern['%Y-%m-%d %H:%M:%S']]
    created_at:DateTimePattern['%Y-%m-%d %H:%M:%S']
    updated_at:Optional[DateTimePattern['%Y-%m-%d %H:%M:%S']]
    state_timestamp:Optional[DateTimePattern['%Y-%m-%d %H:%M:%S']]
    created_by:int
    updated_by:Optional[int]
    chip_id:Optional[int]
    gsm_number:Optional[str]
    gnss_version:Optional[str]
    login_count:int
    parameter_collect:Optional[str]
    last_sync:DateTimePattern['%Y-%m-%d %H:%M:%S']
    iccid:str
    imsi:str
    ble_firmware:str
    sold_at:DateTimePattern['%Y-%m-%d %H:%M:%S']
    shipment:str
    last_analytics_received_at:DateTimePattern['%Y-%m-%d %H:%M:%S']
    product_code:str
    company_name:Optional[str]
    group_name:Optional[str]
    next_task:Optional[str]
    can_adapter:Optional[str]
    obd:Optional[str]
    accessories:Optional[str]
    carrier:Optional[str]
    company:Optional[FotaCompany]
    group:Optional[FotaGroup]
    activity_status:str
    task_queue:str
    modem_version:Optional[str]
    model_platform:str

    def __str__(self):
        return f"{self.imei}:{self.model}"

Here's two records lightly sanitised from the collection so you can see the source data:

[
    {
        "imei": 1111111,
        "serial": 111,
        "model": "FMM001",
        "spec_id": 1,
        "platform_id": 1,
        "current_configuration": null,
        "current_firmware": "03.27.13.Rev.54",
        "description": "xxxxxx",
        "company_id": 13991,
        "group_id": null,
        "track": 6,
        "first_login": "2022-11-09 02:08:20",
        "seen_at": "2024-02-07 22:29:28",
        "created_at": "2021-10-18 09:14:06",
        "updated_at": "2024-02-07 22:29:28",
        "state_timestamp": null,
        "created_by": 10,
        "updated_by": 1,
        "chip_id": null,
        "gsm_number": "6141111",
        "gnss_version": null,
        "login_count": 1,
        "parameter_collect": null,
        "last_sync": "2024-02-01 09:55:25",
        "iccid": "8961111111111111",
        "imsi": "111111111q111",
        "ble_firmware": null,
        "sold_at": "2021-11-10 00:00:00",
        "shipment": "LTG172",
        "last_analytics_received_at": null,
        "product_code": "FMM001FPSP01",
        "company_name": "xxxxxxxxxxx",
        "group_name": null,
        "next_task": null,
        "can_adapter": null,
        "obd": null,
        "accessories": null,
        "carrier": null,
        "company": {
            "code": "SG3414",
            "id": 13991,
            "name": "xxxxxxxxxx",
            "company_id": 37,
            "deleted_at": null,
            "created_at": "2021-02-16 03:57:26",
            "updated_at": "2023-06-12 09:21:35",
            "created_by": 1,
            "updated_by": 11239
        },
        "group": null,
        "activity_status": "Offline",
        "task_queue": "Empty",
        "modem_version": null,
        "model_platform": "Fmx"
    },
    {
        "imei": 2222222222,
        "serial": 2222,
        "model": "FMM001",
        "spec_id": 1,
        "platform_id": 1,
        "current_configuration": null,
        "current_firmware": "03.27.07.Rev.00",
        "description": "xxxxxxx",
        "company_id": 13991,
        "group_id": null,
        "track": 6,
        "first_login": "2022-11-09 01:56:02",
        "seen_at": "2023-02-22 01:00:37",
        "created_at": "2021-10-18 09:14:06",
        "updated_at": "2023-09-18 02:18:18",
        "state_timestamp": null,
        "created_by": 10,
        "updated_by": 8225,
        "chip_id": null,
        "gsm_number": "61473914722",
        "gnss_version": null,
        "login_count": 1,
        "parameter_collect": null,
        "last_sync": "2023-02-02 04:22:21",
        "iccid": "89622222222222",
        "imsi": "2222222222",
        "ble_firmware": null,
        "sold_at": "2021-11-10 00:00:00",
        "shipment": "LTG172",
        "last_analytics_received_at": null,
        "product_code": "FMM001FPSP01",
        "company_name": "xxxxxxx",
        "group_name": null,
        "next_task": null,
        "can_adapter": null,
        "obd": null,
        "accessories": null,
        "carrier": null,
        "company": {
            "code": "SG3414",
            "id": 13991,
            "name": "xxxxxxx",
            "company_id": 37,
            "deleted_at": null,
            "created_at": "2021-02-16 03:57:26",
            "updated_at": "2023-06-12 09:21:35",
            "created_by": 1,
            "updated_by": 11239
        },
        "group": null,
        "activity_status": "Offline",
        "task_queue": "Empty",
        "modem_version": null,
        "model_platform": "Fmx"
    },
    
]

Logically the error is on a datetime field, which is why I've wrapped them as Optional

I've added debugging to the class header, and I don't understand the output. It seems to imply that every field has a missing type? Newlines on Field( added by me:

DEBUG:dataclass_wizard:Globals before function compilation: {'cls_fields': (
Field(name='imei',type=<class 'int'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='serial',type=<class 'int'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='model',type=<class 'str'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='spec_id',type=<class 'int'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='platform_id',type=<class 'int'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='current_configuration',type=typing.Optional[str],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='current_firmware',type=<class 'str'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='description',type=typing.Optional[str],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='company_id',type=<class 'int'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='group_id',type=typing.Optional[int],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='track',type=<class 'int'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='first_login',type=typing.Optional[PatternedDT(cls=<class 'datetime.datetime'>, pattern='%Y-%m-%d %H:%M:%S')],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='seen_at',type=typing.Optional[PatternedDT(cls=<class 'datetime.datetime'>, pattern='%Y-%m-%d %H:%M:%S')],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='created_at',type=PatternedDT(cls=<class 'datetime.datetime'>, pattern='%Y-%m-%d %H:%M:%S'),default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='updated_at',type=typing.Optional[PatternedDT(cls=<class 'datetime.datetime'>, pattern='%Y-%m-%d %H:%M:%S')],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='state_timestamp',type=typing.Optional[PatternedDT(cls=<class 'datetime.datetime'>, pattern='%Y-%m-%d %H:%M:%S')],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='created_by',type=<class 'int'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='updated_by',type=typing.Optional[int],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='chip_id',type=typing.Optional[int],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='gsm_number',type=typing.Optional[str],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='gnss_version',type=typing.Optional[str],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='login_count',type=<class 'int'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='parameter_collect',type=typing.Optional[str],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='last_sync',type=PatternedDT(cls=<class 'datetime.datetime'>, pattern='%Y-%m-%d %H:%M:%S'),default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='iccid',type=<class 'str'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='imsi',type=<class 'str'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='ble_firmware',type=<class 'str'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='sold_at',type=PatternedDT(cls=<class 'datetime.datetime'>, pattern='%Y-%m-%d %H:%M:%S'),default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='shipment',type=<class 'str'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='last_analytics_received_at',type=PatternedDT(cls=<class 'datetime.datetime'>, pattern='%Y-%m-%d %H:%M:%S'),default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='product_code',type=<class 'str'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='company_name',type=typing.Optional[str],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='group_name',type=typing.Optional[str],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='next_task',type=typing.Optional[str],default=<dataclasses._MISSING_TYPE object at 0x00,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='accessories',type=typing.Optional[str],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='carrier',type=typing.Optional[str],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='company',type=typing.Optional[fleetlogix.fota.FotaCompany],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='group',type=typing.Optional[fleetlogix.fota.FotaGroup],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='activity_status',type=<class 'str'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='task_queue',type=<class 'str'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='modem_version',type=typing.Optional[str],default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD), 
Field(name='model_platform',type=<class 'str'>,default=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,default_factory=<dataclasses._MISSING_TYPE object at 0x000001507F56E180>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),kw_only=False,_field_type=_FIELD)), 'LOG': <Logger dataclass_wizard (DEBUG)>, 'MissingData': <class 'dataclass_wizard.errors.MissingData'>, 'MissingFields': <class 'dataclass_wizard.errors.MissingFields'>, 'ParseError': <class 'dataclass_wizard.errors.ParseError'>}
DEBUG:dataclass_wizard:Namespace after function compilation: {'cls_fromdict': <function __create_cls_fromdict_fn__.<locals>.cls_fromdict at 0x000001500106D300>}

What I'm trying to find is the definitive field causing the error

I see 'last_analytics_received_at is described as datetime.datetime field, but gets null instead. — strawdog
– strawdog, Commented Jul 9 at 8:53
As for your porblem: clearly one of the fields receiving a datetime is not properly marked as optional - the message is explicit in saying it got a None. Presumably, the dataclass-wizard tooling you are using should make it work if it was marked as optional. — jsbueno
– jsbueno, Commented Jul 9 at 13:34

Hecatonchires · Accepted Answer · 2025-07-10 05:54:46Z

0

I hadn't wrapped all the datetimes. I also had to create a few subclasses for items that I initially thought were just strings.

answered Jul 10 at 5:54

Hecatonchires

1,1214 gold badges19 silver badges45 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Find field throwing error in Python Dataclass conversion

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related