lora.callback with arguments

[James Hofer]

Summary:

• Does the Lora callback accept arguments?

• Is this alternate solution problematic or present other considerations?

I can not seem to successfully pass arguments as the documentation suggests is possible.
Documentation (link): lora.callback(trigger, [handler=None, arg=None])

Documentation Example (without args):

def lora_cb(lora):
    ...

lora.callback(trigger=(LoRa.RX_PACKET_EVENT | LoRa.TX_PACKET_EVENT), handler=lora_cb)

Tried:

def lora_cb(lora, arg):
    ...

lora.callback(trigger=(LoRa.RX_PACKET_EVENT | LoRa.TX_PACKET_EVENT), handler=lora_cb, arg=tx)

TypeError: function takes 2 positional arguments but 1 were given

Does lora.callback accept arguments?
After failing, I stumbled across a workaround for a callback that doesn't accept arguments: solution.

TX_CNT = 0
RX_CNT = 0

def lora_cb(lora, TX, RX):
    events = lora.events()
    if events & LoRa.RX_PACKET_EVENT:
        print('recv {}'.format(RX))
    if events & LoRa.TX_PACKET_EVENT:
        print('sent {}'.format(TX))

callback_lambda = lambda x: lora_cb(x, TX_CNT, RX_CNT)
lora.callback(trigger=(LoRa.RX_PACKET_EVENT | LoRa.TX_PACKET_EVENT), handler=callback_lambda)

Implementing a callback of a callback does seem to work, but I'm confused as to the implications of this solution.
For example, what if I wanted to return something back up the call chain.
Can someone clarify or point me to some info that I can read up on what is going on?

[James Hofer]

Update: eventually using globals as jcaron suggested was the solution (by-passing the need for argument passing).

[James Hofer]

@jcaron Thanks for the reply. Maybe it is scoping, I'll try some more examples and post back.

I'm trying to have a main app loop that is not Lora-related but can respond to Lora events (by send/rcv data).

[jcaron]

@James-Hofer strangely enough, if you pass a value as arg, it will become the only argument passed to the callback, instead of the LoRa object, rather than in addition to it.

But it’s unclear to me what exactly you are trying the achieve. I think you just have a scope issue, maybe simply specifying the variables you need to access as global, or using an enclosing scope, would do what you want?