The to_list operator converts an observable sequence to a single item that contains all the items emitted by the source observable, wrapped in a list. The following figure shows the marble diagram of this operator:

Its prototype is the following:

numbers = Observable.from_([1, 2, 3, 4])

numbers.to_list().subscribe(
    on_next = lambda i: print("on_next {}".format(i)),
    on_error = lambda e: print("on_error: {}".format(e)),
    on_completed = lambda: print("on_completed")
)

This example gives the following result:

on_next [1, 2, 3, 4]
on_completed

Only one item is received, containing the source sequence as a list.

There are several variants of this operator:

• to_set converts a sequence to a set
• to_dict converts a sequence to a dictionary