Define named constants in Python and explain their purpose. Illustrate with an example how usingnamed constants can make a program more readable and maintainable, such as in a scientificcalculation.

Named constants in Python are variables whose values are set only once and cannot be changed throughout the program. They are used to provide meaningful names to data that is used in the program, making the code more readable and maintainable.

In Python, constants are usually declared and assigned on a module. Here, the constant is created by assigning a value to a variable at the top of the script. Once this is done, the constant can be used in the rest of the code. However, Python doesn’t support constants natively. Therefore, by convention, we use all capital letters to declare a variable as a constant.

For example, consider a scientific calculation where we need to use the value of PI. Instead of using the numerical value of PI (3.14159) every time we need it in the calculations, we can declare a named constant at the beginning of the program:

PI = 3.14159

Then, we can use this named constant in our calculations:

def calculate_circumference(radius):
    return 2 * PI * radius

This makes the code more readable because when someone else reads the code, they immediately know what PI is. It also makes the code more maintainable because if we need to change the value of PI (for example, to add more decimal places), we only need to change it in one place.