How to Count the Number of Elements in a Python List

May 21, 2021

The len() function can be used to count the number of elements in a Python list:

len(my_list)

In this short guide, you’ll see 3 examples of counting the number of elements in:

  1. List that contains strings
  2. List that includes numeric data
  3. List of lists

(1) Count the Number of Elements in a Python List that Contains Strings

To start with a simple example, let’s create a list that contains 5 names:

names_list = ['Jeff', 'Ben', 'Maria', 'Sophia', 'Rob']
print(names_list)

Run the syntax above, and you’ll get the following list:

['Jeff', 'Ben', 'Maria', 'Sophia', 'Rob']

You can then use the len() function in order to count the number of elements in the list:

names_list = ['Jeff', 'Ben', 'Maria', 'Sophia', 'Rob']
print(len(names_list))

Once you run the code in Python, you’ll get the count of 5.

Let’s extend the list by additional 3 names, and then recount the number of elements:

names_list = ['Jeff', 'Ben', 'Maria', 'Sophia', 'Rob']
names_list.extend(['Laura','Elizabeth','Justin'])
print(len(names_list))

You’ll now get the count of 8.

(2) Count the Number of Elements in a Python List that Includes Numeric Data

Let’s now create a list with numeric data:

numbers_list = [7,22,35,28,42,15,30,11,24,17]
print(numbers_list)

Here is the list that you’ll get:

[7, 22, 35, 28, 42, 15, 30, 11, 24, 17]

To count the number of elements in the list, use the len() function:

numbers_list = [7,22,35,28,42,15,30,11,24,17]
print(len(numbers_list))

You’ll get the count of 10.

(3) Count the Number of Elements in a List of Lists

What if you want to count the number of elements in a list of lists?

For instance, let’s create the following list of lists:

people_list = [['Jon','Smith',21],['Mark','Brown',38],['Maria','Lee',42],['Jill','Jones',28],['Jack','Ford',55]]
print(people_list)

You’ll now see this list of lists:

[['Jon', 'Smith', 21], ['Mark', 'Brown', 38], ['Maria', 'Lee', 42], ['Jill', 'Jones', 28], ['Jack', 'Ford', 55]]

Before you count all the elements, you’ll need to flatten the list of lists as follows:

people_list = [['Jon','Smith',21],['Mark','Brown',38],['Maria','Lee',42],['Jill','Jones',28],['Jack','Ford',55]]
flat_people_list = [i for x in people_list for i in x]
print(flat_people_list)

Here is how the flatten list would look like:

['Jon', 'Smith', 21, 'Mark', 'Brown', 38, 'Maria', 'Lee', 42, 'Jill', 'Jones', 28, 'Jack', 'Ford', 55]

Finally, you can use the code below to get the total count:

people_list = [['Jon','Smith',21],['Mark','Brown',38],['Maria','Lee',42],['Jill','Jones',28],['Jack','Ford',55]]
flat_people_list = [i for x in people_list for i in x]
print(len(flat_people_list))

Once you run the code, you’ll get the count of 15.