Python Constants

In Python, a constant is a value that cannot be changed once it's been assigned. Constants are used to represent fixed values that are used throughout a program, such as mathematical constants or predefined configurations.

In Python, there is no built-in support for constants, but there are several ways to create them. One way is to use all uppercase letters for the variable name. This is a convention that is widely used in the Python community to indicate that a variable should be treated as a constant. For example,

1PI = 3.14  # a mathematical constant

Create constant variable using constant module

Another way to create constants is to use the constant module. The constant module is not built-in, but it can be installed using pip. Once you have installed it, you can use it to define constants like this:

1from constant import Constant
2
3class MyConstants(Constant):
4    PI = 3.14
5    GRAVITY = 9.8
6
7print(MyConstants.PI)  # Output: 3.14

In this example, we define a class MyConstants that inherits from the Constant class, and we define two constants PI and GRAVITY as class variable.

It's important to note that, even though constants are defined as uppercase variable names or with the help of a module, Python does not prevent you from reassigning the value to a variable that is intended to be a constant.

When naming constants, it's a good practice to use all uppercase letters and separate words with an underscore. This makes it clear that the variable is a constant, and

  • Using all uppercase letters for the variable name is a convention that is widely used in the Python community to indicate that a variable should be treated as a constant, but Python does not actually enforce this.
  • Some developers use a global variable with the constant module, and some use a class variable.
  • Constants are usually used to represent fixed values that are used throughout a program, such as mathematical constants, predefined configurations or some other values that should not be modified.
  • In some cases, it can also make sense to use constants to define values that are unlikely to change but are not strictly fixed, like a default configuration value.
  • Constants can also be used to improve the readability of code, by providing more meaningful names for values that are used in multiple places.

In summary, constants are used to represent fixed values in Python. They are not enforced by the language, but it's a good practice to use all uppercase letters and separate words with an underscore to indicate that a variable should be treated as a constant. They can be defined using a global variable with the constant module or using a class variable. Constants can be used to improve the readability of code, by providing more meaningful names for values that are used in multiple places or to represent fixed values that are used throughout a program like mathematical constants or predefined configurations.