I don’t do python very often but just playing with a raspberry pi pico, so I’m using micropython
I have an instance of an object that I want to serialise as json to send to a backend.

class Heartbeat:
    def __init__(self, batteryVoltage, batteryCurrent, batteryPercentage):
        self.type = 'heartbeat'
        self.batteryVoltage = batteryVoltage
        self.batteryCurrent = batteryCurrent
        self.batteryPercentage = batteryPercentage

I create an instance of this, and then call json.dumps, expecting to receive something along the lines of

{
‘type’: ‘heartbeat’, ‘batteryVoltage’: 90, ‘batteryCurrent’: 0.123, ‘batteryPercentage’: 99
}

The code is

import json
from Heartbeat import Heartbeat

...

heartbeatData = Heartbeat(bus_voltage, (current/1000), P)
message = json.dumps(heartbeatData)
print(message)

The print is output as:

<Heartbeat object at 2001e350>

Which is not what I assumed json.dumps(heartbeat) would return, its just printing the reference to the object

See above, a stringified version of the object