Python get size of list

Question

In Python, you use a list to store various types of data such as strings and numbers.

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How to Get the Length of a List with the len() Function
How to Get the Length of a List with the length_hint() Function
Final Thoughts
How do you find the length of a list?
How do you find the length of a list without using Len in Python?
How do you print the number of items in a list in Python?

A list is identifiable by the square brackets that surround it, and individual values are separated by a comma.

To get the length of a list in Python, you can use the built-in len() function.

Apart from the len() function, you can also use a for loop and the length_hint() function to get the length of a list.

In this article, I will show you how to get the length of a list in 3 different ways.

You can use the native for loop of Python to get the length of a list because just like a tuple and dictionary, a list is iterable.

This method is commonly called the naïve method.

The example below shows you how to use the naïve method to get the length of a list in Python

demoList = ["Python", 1, "JavaScript", True, "HTML", "CSS", 22]

# Initializing counter variable
counter = 0

for item in demoList:
    # Incrementing counter variable to get each item in the list
    counter = counter + 1

    # Printing the result to the console by converting counter to string in order to get the number
print("The length of the list using the naive method is: " + str(counter))
# Output: The length of the list using the naive method is: 7

How to Get the Length of a List with the len() Function

Using the len() function is the most common way to get the length of an iterable.

This is more straightforward than using a for loop.

The syntax for using the len() method is len(listName).

The code snippet below shows how to use the len() function to get the length of a list:

demoList = ["Python", 1, "JavaScript", True, "HTML", "CSS", 22]

sizeOfDemoList = len(demoList)

print("The length of the list using the len() method is: " + str(sizeOfDemoList))
# Output: The length of the list using the len() method is: 7

How to Get the Length of a List with the length_hint() Function

The length_hint() method is a less known way of getting the length of a list and other iterables.

length_hint() is defined in the operator module, so you need to import it from there before you can use it.

The syntax for using the length_hint() method is length_hint(listName).

The example below shows you how to use the length_hint() method to get the length of a list from operator import length_hint:

demoList = ["Python", 1, "JavaScript", True, "HTML", "CSS", 22]

sizeOfDemoList = length_hint(demoList)
print("The length of the list using the length_hint() method is: " + str(sizeOfDemoList))
# The length of the list using the length_hint() method is: 7

Final Thoughts

This article showed you how to get the size of a list with 3 different methods: a for loop, the len() function, and the length_hint() function from the operator module.

You might be wondering which to use between these 3 methods.

I would advise that you use len() because you don't need to do much to use it compared to for loop and length_hint().

In addition, len() seems to be faster than both the for loop and length_hint().

If you find this article helpful, share it so it can reach others who need it.

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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

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:

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).

How to check if a list is empty in Python

How do you find the length of a list?

Len() Method There is a built-in function called len() for getting the total number of items in a list, tuple, arrays, dictionary, etc. The len() method takes an argument where you may provide a list and it returns the length of the given list.