Extracting Ones from an Integer Using the Modulo Operator

In this post, I'll discuss an uncommon use case for the modulo operator: extracting ones from an integer. Let's say we have a variable that is of type Integer and we we want to know how many ones there are. For example, the number 12 has 2 ones. How do we extract the ones digit? The inefficient way to do this would be to convert the integer to a string, grab the last character from the string, and then convert it back to an integer like this:

integer = 555

# Inefficient way - don't do this
ones_string = str(integer)[-1]
ones = int(ones_string)

Fortunately, there's a more elegant and efficient solution. You can use the modulo operator to obtain the ones digit directly, as follows:

# Efficient way - do this
ones = integer % 10

By taking the remainder when dividing the integer by 10, we effortlessly isolate the ones digit. This method not only simplifies the task but also improves code readability and performance.