The of operator is a variant of the from_ operator. This operator creates an observable from a variable number of arguments. The marble diagram of this operator is shown in the following diagram:

Its prototype is as follows:

Observable.of(*args, **kwargs)

The scheduler can be provided as the optional scheduler keyword argument. This operator can be used with values directly passed to it, as follows:

numbers = Observable.of(1, 2, 3, 4)
numbers.subscribe(
        on_next=lambda i: print("item: {}".format(i)),
        on_error=lambda e: print("error: {}".format(e)),
        on_completed=lambda: print("completed")
    )

Upon subscription, the sequence provided as the argument of the of operator is emitted on the observable before it completes, as follows:

item: 1
item: 2
item: 3
item: 4
completed

The of operator can also be used to create an observable from the arguments of a function. The following example returns the same values as the previous one:

def create_numbers_observable(*args):
    return Observable.of(*args)

create_numbers_observable(1, 2, 3, 4).subscribe(
        on_next=lambda i: print("item: {}".format(i)),
        on_error=lambda e: print("error: {}".format(e)),
        on_completed=lambda: print("completed")
    )