Hands-On Reactive Programming with Python

The start_with operator

The start_with operator emits items on the output observable before any other item of the source observable. The marble diagram of this operator follows:

Figure 8.5: The start_with operator

The prototype of this operator is the following:

Observable.start_with(self, *args, **kw)

The args parameter contains the items to emit prior to any other one. Optionally, the first argument can be a scheduler. A scheduler can also be provided with the scheduler keyword argument.

The start_with operator can be used this way:

numbers = Observable.from_([1, 2, 3, 4])numbers.start_with(0).subscribe( on_next = lambda i: print("on_next ...