Python BasicsPython Basics11
❯
  1. 1Introduction to Python
  2. 2Python Hello World Program
  3. 3Python Comments
  4. 4Python Variables
  5. 5Python Constants
  6. 6Python Data Types
  7. 7Python Strings
  8. 8Python Type Conversions
  9. 9Python Basic Input and Output
  10. 10Python Operators
  11. 11Python Operator Precedence
Python Flow ControlPython Flow Control5
❯
  1. 1Python Conditional Statements
  2. 2Python Loops
  3. 3Python For Loop
  4. 4Python While Loop
  5. 5Python Break and Continue
Python CollectionsPython Collections5
❯
  1. 1Python Collections
  2. 2Python Lists
  3. 3Python Dictionaries
  4. 4Python Tuples
  5. 5Python Sets
Python FunctionsPython Functions4
❯
  1. 1Python Functions
  2. 2Python Functions with Parameters
  3. 3Python main() Function
  4. 4Python Lambda Functions
Python File HandlingPython File Handling1
❯
  1. 1Python File Operations
Python Exception HandlingPython Exception Handling3
❯
  1. 1Python Exceptions
  2. 2Python Exception Handling
  3. 3Python Custom Exceptions
Python OOPsPython OOPs5
❯
  1. 1Python Object-Oriented Programming
  2. 2Python Inheritance
  3. 3Python Multiple Inheritance
  4. 4Python Encapsulation
  5. 5Python Polymorphism
Python Advanced ConceptsPython Advanced Concepts5
❯
  1. 1Python List Comprehension
  2. 2Python Iterators
  3. 3Python Generators
  4. 4Python Closures
  5. 5Python Decorators
Python LibrariesPython Libraries3
❯
  1. 1Python Email Tutorial
  2. 2Python JSON Tutorial
  3. 3Python datetime Tutorial
Python ReferencePython Reference2
❯
  1. 1Python Built-in Functions
  2. 2Python String Methods

Python Constants

Constants

In Python, a constant is a value that should not change once it's been given. For example, if you have a value like the number of days in a week, it always stays the same: 7.

While Python doesn't have a special way to make real constants (like some other languages do), we can still follow a naming rule to show that something is meant to stay the same.

How to Create a Constant in Python

We usually use capital letters for constant names, like this:

DAYS_IN_WEEK = 7
PI = 3.14
APP_NAME = "MyFirstApp"

These are all constants. The capital letters tell us, “Hey! Don’t change this value.”

{ "array": ["7", "3.14", "MyFirstApp"], "showIndices": false, "highlightIndicesBlue": [0], "highlightIndices": [1], "highlightIndicesGreen": [2], "labels": { "0": "DAYS_IN_WEEK", "1": "PI", "2": "APP_NAME" } }

Using Constants

DAYS_IN_WEEK = 7
print("There are", DAYS_IN_WEEK, "days in a week.")
There are 7 days in a week.

Explanation: We created a constant DAYS_IN_WEEK and printed its value along with some text. The value 7 was shown because that’s what we stored in it.

What Happens If We Change a Constant?

PI = 3.14
print("Original PI:", PI)

PI = 3.14159  # changing the value
print("Changed PI:", PI)
Original PI: 3.14
Changed PI: 3.14159

Explanation: Python let us change the value, even though we wrote it as a constant. But this is not a good habit. Constants are called that because we should not change them.

So, it's our responsibility as programmers to treat them like fixed values and not update them later.

Tips for Using Constants

  • Use capital letters with underscores: MAX_SPEED, API_KEY, PI
  • Put constants at the top of your Python file so they are easy to find
  • Don’t change their values once they’re set

Conclusion

Constants are values that we decide should not change. Python doesn’t force them to stay constant, but we follow rules to treat them that way.