In Python, List is a collection data-type which is ordered and changeable. A list can have duplicate entry as well. Here, the task is find the number of entries in a list. See the examples below.
Examples:
Input : a = [1, 2, 3, 1, 2, 3] Output : 6 Count the number of entries in the list a. Input : a = [] Output : 0
The idea is to use len() in Python
# Python program to demonstrate working # of len() a = [] a.append("Hello") a.append("Geeks") a.append("For") a.append("Geeks") print("The length of list is: ", len(a))
Output:
The length of list is: 4
Example 2:
# Python program to demonstrate working # of len() n = len([10, 20, 30]) print("The length of list is: ", n)
Output:
The length of list is: 3
How does len() work?
len() works in O(1) time as list is an object and has a member to store its size. Below is description of len() from Python docs.
Return the length (the number of items) of an object. The argument may be a sequence (such as a string, bytes, tuple, list, or range) or a collection (such as a dictionary, set, or frozen set).