Variables
A Python variable is simply a name (a label) you use to refer to a value (the information). It allows you to store, retrieve, and change data in your program in an organized way.
Creating Variables
Creating a variable is simple in Python. You just give it a name and use the equals sign (
=) to put a value inside the “box”.
Syntax (The Rule):
variable_name = value | Example | What it does (Box Analogy) |
age = 30 |
Creates a box labeled age and puts the number 30 inside. |
name = "Sara" |
Creates a box labeled name and puts the text “Sara” inside. |
is_sunny = True |
Creates a box labeled is_sunny and puts the value True inside. |
Variable Names
A variable can have a short name (like
a and b) or a more descriptive name (age, name, total_number). Golden Rules for Naming Variables
- A variable name must start with a letter or the underscore character.
- A variable name cannot begin with a number.
- A variable name can only contain alphanumeric characters and underscores (A-z, 0-9, and _).
- Variable names are case-sensitive (e.g.,
age,Age, andAGEare three different variables). - Cannot be one of Python’s reserved words (like
if,for,while, etc.).
Example
user_age = 30
high_score = 9875
daily_temp = 25.5
item_price = 49.99
first_name = "Jamie"
website_url = "www.estudy247.com"
status_message = "Order Shipped"
is_active = True
has_discount = False
total_amount_2 = 150
MAX_CAPACITY = 5000
_temp_var = "Internal data"
Key Concepts for Variables
1. Variables are Dynamic (They Can Change!)
A variable is not set in stone. You can change the value in the “box” whenever you need to.
- Start:
score = 100(Thescorebox holds 100) - Change:
score = 150(Thescorebox now holds 150. The old value 100 is forgotten.)
You can even change the type of information a variable holds (though this is often avoided in professional code, Python allows it).
- Change Type:
data = 5(Holds a number) –>data = "hello"(Now holds text)
2. Data Types (What's in the Box?)
The type of value a variable holds is called its Data Type. Python figures this out automatically.
The three main types you’ll use are:
The three main types you’ll use are:
| Type | Layman’s Term | Python Name | Example |
| Whole Numbers | Integers | int | 10, -5, 0 |
| Text | Strings (anything inside quotes) | str | "Hello", "30", "A" |
| True/False | Booleans | bool | True, False |
3. What is a Global Variable?
In Python, variables have different scopes, which simply means where they are visible or where they can be used.
- A Global Variable is a variable defined in the main body of your Python script (outside of any specific function).
- Think of it as a central bulletin board available to everyone in the office (your entire program). Any function or piece of code can read its value.
Example
MAX_PLAYERS = 50 # This is a Global Variable
def check_limit(new_players):
# This function can READ MAX_PLAYERS without any special keywords.
if new_players > MAX_PLAYERS:
print("Limit reached!")