So far, in the examples that I've presented earlier, we've only dealt with cases where there has only been one Observable and one Observer. However, one of the most powerful aspects of the RxPY library is the fact that our observables can multicast emissions out to numerous subscribers.
The need for multicasting comes from the fact that having multiple subscribers subscribe to the one observable would result in discrepancies with regards to the events that both of these subscribers receive. However, using multicasting, we can effectively eliminate these discrepancies and ensure that all of our subscribers, regardless of how many we have, will receive identical events.
Take, for instance, the following lines of code:
from rx import Observable
from random import randint
three_emissions = Observable.range(1, 3)
three_random_ints = three_emissions.map(lambda i: randint(1, 100000))
three_random_ints.subscribe(lambda i: print("Subscriber 1 Received: {0}".format(i)))
three_random_ints.subscribe(lambda i: print("Subscriber 2 Received: {0}".format(i)))
This code features a simple observable that emits three random events, each containing a generated random number that ranges anywhere from 1 to 100,000. If we were then to execute the preceding code, you may have expected to see both subscriber 1 and subscriber 2 receive the same events. However, if we have a look at the output of the said program, you'll see this isn't the case:
$ python3.6 03_multicast.py
Subscriber 1 Received: 21097
Subscriber 1 Received: 19863
Subscriber 1 Received: 68053
Subscriber 2 Received: 69670
Subscriber 2 Received: 11348
Subscriber 2 Received: 8860
