Hands-On Reactive Programming with Python

The group_by operator

The group_by operator groups items of the source observable, where the groups are determined by a selector function. This operator returns a higher-order observable. The following figure shows the marble diagram of this operator:

Figure 9.3: The group_by operator

The prototype of this operator is the following:

group_by(self, key_selector, element_selector=None,        key_serializer=None)

Here, key_selector is a function that returns a key from an item. This key is used to group items per key. The optional element_selector parameter is a function used to map each source item in the observable of the group. Its default value ...