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In this article, the editor introduces in detail "how to achieve the iterator pattern in python". The content is detailed, the steps are clear, and the details are handled properly. I hope this article "how to implement the iterator pattern in python" can help you solve your doubts.

Code example

Because the iterator is already the standard equipment of many languages, in the actual development, we should first consider the iterator provided in the language, and define our own browser according to the iterator interface defined by the language when the function can not meet the requirements. Next, we illustrate the application of several iterator patterns through the example of Python language.

A variety of containers, such as lists and dictionaries, have been defined in advance in the Python language. Each of these containers provides an iter method to get the iterator. Let's use an iterator in the Python language to implement the representation of an aggregate class and its child elements.

A list is defined internally in aggregation class 1 to manage subordinate child elements. Aggregate class 2 does not contain subordinate child elements, but has three data members. These two classes implement the iter method respectively, where aggregate class 1 returns the iterator of the list in the Python language, and aggregate class 2 does not contain subordinate members, so it returns a dictionary of data members in its iterator method. Once the iterator method is ready, users can use the same iterator method to access two aggregation classes that are implemented in completely different ways.

You can see that the data members of aggregation class 2 are output in the order in which the data members are defined. In actual development, you sometimes want the data members to be output in a different order. At this point, you need to define your own iterator.

The above code is an example of aggregating classes using iterators to access different data structures. You can also use a combination of iterators to achieve different ways of access. For example, the following code uses the same algorithm to sum the values in the list and dictionary, respectively.

We can also define another iterator to filter the data in the container:

Through the combination of this iterator and the existing iterator, we can filter the data without changing the algorithm or the data structure.

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