Python's Counter: The Pythonic Way to Count Objects – Real Python

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Watch Now This tutorial has a related video course created by the Real Python team. Watch it together with the written tutorial to deepen your understanding: Counting With Python's Counter

Counting several repeated objects at once is a common problem in programming. Python offers a bunch of tools and techniques you can use to approach this problem. However, Python’s Counter from collections provides a clean, efficient, and Pythonic solution.

This dictionary subclass provides efficient counting capabilities out of the box. Understanding Counter and how to use it efficiently is a convenient skill to have as a Python developer.

In this tutorial, you’ll learn how to:

Count several repeated objects at once
Create counters with Python’s Counter
Retrieve the most common objects in a counter
Update object counts
Use Counter to facilitate further computations

You’ll also learn about the basics of using Counter as a multiset, which is an additional feature of this class in Python.

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Counting Objects in Python

Sometimes you need to count the objects in a given data source to know how often they occur. In other words, you need to determine their frequency. For example, you might want to know how often a specific item appears in a list or sequence of values. When your list is short, counting the items can be straightforward and quick. However, when you have a long list, counting things can be more challenging.

To count objects, you typically use a counter, which is an integer variable with an initial value of zero. Then you increment the counter to reflect the number of times a given object appears in the input data source.