How to call/start a thing?

I use a Item with {channel=“exec:command:xxx:output”} and a
Thing exec:command:xxx [command=“xxx”, interval=10]. It works.
Now I wont to start/call the Thing in special situations from a Rule immediately or maybe change the interval to 1 and back afterwards.
How can I do?

To run it immediately you just sendCommand(ON) to an Item linked to the run Channel.

You cannot change the interval dynamically. You can remove the interval and use a Rule with Timers to control how often the script runs.

String pcf8574t_21_8o <switch> (pcf8574_o,i2c) {channel="exec:command:pcf8574tT21_8o:output"}
Thing exec:command:pcf8574tT21_8o [command="python /etc/openhab2/scripts/ 0x21 8", interval=10]

sendCommand changes the state, but the Thing was not executed immediately, but after expiration the interval.

I don’t use Exec binding much. It may be the case that you can’t sendCommand to cause the script to run if you have an interval.

But if all you have is the Thing and Item you posted above, you didn’t follow my instructions.

You need to create a new Switch Item linked to the run channel of the Thing. Sending a command to the output channel will do nothing.

Switch exec_pcf8574t_21_80 <switch> { channel="exec:command:pcf8574tT21_80:run" }

Note: these are really horrible names for Items and Things. You should be modeling and naming thing for what they are, like LivingRoom_Lamp, not some serial number for a relay. That is one of the main points with Items. It is supposed to abstract away the hardware so you can focus on the behavior of your home. It is easier for you in the long run and easier on us to help understand what you are trying to achieve when we help on the forum.