Python Variables 📦

What is a Variable?

Think of a variable as a label or a sticky note that you attach to a value. Unlike C++ or Java where a variable is a "box" that holds data, in Python, the variable points to where the data is stored in memory.

🤖 Analogy: The Sticky Note

x = 5
Imagine the number 5 is an object sitting on a shelf (memory).
The variable x is just a sticky note with "x" written on it, stuck onto that object.
If you say y = x, you are just putting another sticky note "y" on the same object!

✨ Creating Variables

python

x = 5           # x points to an integer object (5)
y = "John"      # y points to a string object ("John")
print(x)
print(y)

🔧 Under the Hood: Memory Addresses

You can see where an object lives in memory using the id() function.

python

x = 10
y = 10

print(id(x))
print(id(y))
# Output: Same number! Python optimizes small integers by reusing them.

🔄 Dynamic Typing

Python is dynamically typed. This means you don't need to declare the type of a variable (like int x = 5). Variables can even change type after they have been set.

python

x = 4       # x is of type int
x = "Sally" # x is now of type str
print(x)

🏷️ Variable Naming Rules (PEP 8)

A variable can have a short name (like x) or a descriptive name (age, total_volume).

Must start with a letter or the underscore character.
Cannot start with a number.
Can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ ).
Case-sensitive (age, Age and AGE are different variables).

✨ Best Practice: Snake Case

Python developers use snake_case for variable names (all lowercase with underscores).

python

my_variable_name = "John"  # ✅ Good (Pythonic)
myVariableName = "John"    # ❌ Bad (CamelCase is for classes)

🔗 Assign Multiple Values

Many Values to Multiple Variables

python

x, y, z = "Orange", "Banana", "Cherry"
print(x)
print(y)
print(z)

One Value to Multiple Variables

python

x = y = z = "Orange"
print(x)
print(y)
print(z)

📦 Unpacking a Collection

If you have a collection of values in a list, tuple etc. Python allows you to extract the values into variables. This is called Unpacking.

python

fruits = ["apple", "banana", "cherry"]
x, y, z = fruits
print(x)
print(y)
print(z)

💡 Did You Know? Constants

Python doesn't have built-in constant types. By convention, developers use ALL_CAPS to indicate a variable should be treated as a constant and not changed.

python

PI = 3.14159
MAX_CONNECTIONS = 100