How Can I Efficiently Count the Occurrences of an Item in a Python List?

Counting Occurrences of a List Item

Given a specific item from a list in Python, one may seek to determine the number of occurrences of that item within the list. This task can be accomplished using the count method.

Syntax:

list_name.count(item)

Example:

To count the occurrences of the number 1 in the following list:

li = [1, 2, 3, 4, 1, 4, 1]

Use the following code:

li.count(1)

Output:

3

Performance Note:

While the count method is suitable for counting occurrences of a single item, it can be inefficient when counting multiple items. This is because the method iterates over the entire list for each item being counted. If multiple counts are required, it is more efficient to use the Counter class from the collections module, which performs a single iteration over the list to count all elements.

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