shellbot.machines.sequence module

class shellbot.machines.sequence.Sequence(bot=None, machines=None, **kwargs)

Bases: object

Implements a sequence of multiple machines

This implements one state machine that is actually a combination of multiple sub-machines, ran in sequence. When one sub-machine stops, the next one is activated.

Example:

input_1 = Input( ... )
input_2 = Input( ... )
sequence = Sequence([input_1, input_2])
sequence.start()

In this example, the first machine is started, then when it ends the second machine is triggered.

get(key, default=None)

Retrieves the value of one key

Parameters:

• key (str) – one attribute of this state machine instance
• default (an type that can be serialized) – default value is the attribute has not been set yet

This function can be used across multiple processes, so that a consistent view of the state machine is provided.

is_running

Determines if this machine is runnning

Returns:True or False

on_init(**kwargs)

Adds to machine initialisation

This function should be expanded in sub-class, where necessary.

Example:

def on_init(self, prefix='my.machine', **kwargs):
    ...

on_reset()

Adds processing to machine reset

This function should be expanded in sub-class, where necessary.

reset()

Resets a state machine before it is restarted

Returns:True if the machine has been actually reset, else False

This function moves a state machine back to its initial state. A typical use case is when you have to recycle a state machine multiple times, like in the following example:

if new_cycle():
    machine.reset()
    machine.start()

If the machine is running, calling reset() will have no effect and you will get False in return. Therefore, if you have to force a reset, you may have to stop the machine first.

Example of forced reset:

machine.stop()
machine.reset()

run()

Continuously ticks the sequence

This function is looping in the background, and calls the function step() at regular intervals.

The loop is stopped when the parameter general.switch is changed in the context. For example:

bot.context.set('general.switch', 'off')

set(key, value)

Remembers the value of one key

Parameters:

• key (str) – one attribute of this state machine instance
• value (an type that can be serialized) – new value of the attribute

This function can be used across multiple processes, so that a consistent view of the state machine is provided.

start()

Starts the sequence

Returns:either the process that has been started, or None

This function starts a separate thread to run machines in the background.

stop()

Stops the sequence

This function stops the underlying machine and breaks the sequence.