Async Querying

Since the standard query() function is blocking, it can be a hazard for UI event loops. To deal with this, python-OBD has an Async connection object that can be used in place of the standard OBD object.

Async is a subclass of OBD, and therefore inherits all of the standard methods. However, Async adds a few, in order to manage a list of commands and responses. This way, when the user querys the car, the latest response is returned immediately.

import obd

connection = obd.Async() # same constructor as 'obd.OBD()'

connection.watch(obd.commands.RPM) # keep track of the RPM

connection.start() # start the async update loop

print connection.query(obd.commands.RPM) # non-blocking, returns immediately

Callbacks can also be specified, and will return new Responses when available.

import obd
import time

connection = obd.Async() # same constructor as 'obd.OBD()'

# a callback that prints every new value to the console
def new_rpm(r):
    print r.value

connection.watch(obd.commands.RPM, callback=new_rpm)
connection.start()

# the callback will now be fired upon receipt of new values

time.sleep(60)
connection.stop()

Methods

Async.start()

Starts the update loop.

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Async.stop()

Stops the update loop.

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Async.watch(command, callback=None, force=False)

Note: The async loop must be stopped before this function can be called

Subscribes a command to be continuously updated. After calling watch(), the query() function will return the latest Response from that command. An optional callback can also be set, and will be fired upon receipt of new values. Multiple callbacks for the same command are welcome. An optional force parameter will force an unsupported command to be sent.

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Async.unwatch(command, callback=None)

Note: The async loop must be stopped before this function can be called

Unsubscribes a command from being updated. If no callback is specified, all callbacks for that command are dropped. If a callback is given, only that callback is unsubscribed (all others remain live).

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Async.unwatch_all()

Note: The async loop must be stopped before this function can be called

Unsubscribes all commands and callbacks.