In Python, a constant is a variable whose value cannot be changed. Python does not have any built-in keyword to declare a constant. However, you can declare a constant using uppercase letters as variable names or by using the const library in Python 3.10.
Here are examples of both methods to declare and use a constant in Python 3.10:
#### Method 1 - Using Uppercase Letters
PI = 3.14159
RADIUS = 5.0
area = PI * (RADIUS ** 2)
print("The area of the circle is", area)
In this example, PI and RADIUS are declared as constants using uppercase letters. They are then used to calculate the area of the circle. Once the constants are defined they cannot be changed.
#### Method 2 - Using const library
from const import const
# define a constant
MY_CONSTANT = const(10)
# try to change the value of the constant
MY_CONSTANT = 20
print(MY_CONSTANT)
In this example, we are importing the const library to declare a constant. The const function takes an argument for the value of the constant. Once defined, the value of the constant cannot be changed. In this example, MY_CONSTANT is defined as 10, but when we try to change the value to 20, we get an error. When declaring constants using the const library, you cannot change the value after it has been assigned.
I hope this helps!