Variables in Python

Here is a simple and clear explanation of variables in Python 👇

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✅ What is a Variable in Python?

A variable in Python is like a container used to store data.
It holds a value that you can use and change later in your program.

📌 Example:

x = 10
name = "Meenu"
price = 99.50

Here:

• x stores an integer value 10
• name stores a string "Meenu"
• price stores a float 99.50

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✅ Rules for Python Variables

1. Variable names must start with:
   • a letter (a–z or A–Z) or
   • an underscore _
2. They cannot start with numbers
3. They can contain letters, numbers, and underscores

   my_var = 5        ✔️
   2value = 10       ❌ (invalid)
   

4. Variable names are case-sensitive

   age = 10
   Age = 20   # different variable
   

5. No spaces allowed

   user name = "abc"   ❌
   user_name = "abc"   ✔️
   

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✅ Assigning Values to Variables

🔹 Single assignment

a = 5
b = "Hello"

🔹 Multiple assignment

x, y, z = 10, 20, 30

🔹 Same value to multiple variables

a = b = c = 100

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✅ Types of Variables

Python automatically decides the type based on the value:

x = 10          # int
y = 10.5        # float
name = "Meenu"  # str
is_active = True  # bool

To check the type:

print(type(x))

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✅ Changing the value of a variable

Variables can be updated anytime:

x = 10
x = 20   # updated

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⭐ Example Program

name = "Meenu"
age = 20
price = 56.75

print("Name:", name)
print("Age:", age)
print("Price:", price)

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🔥 Python Variables – In Depth

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1️⃣ What Actually Happens When You Create a Variable?

When you write:

x = 10

Python does two things:

1. Creates an object with value 10
2. Creates a variable x that points to that object

📌 Python variables don’t store data directly — they store references (pointers) to memory.

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2️⃣ Variable Naming Styles (Best Practices)

✔ Snake Case (recommended for Python)

user_name = "Meenu"
total_amount = 500

✔ Uppercase (usually used for constants)

PI = 3.14
MAX_LIMIT = 100

❌ Not recommended:

UserName = "abc"
totalAmount = 400    # camelCase is mostly used in JavaScript, not Python

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3️⃣ Dynamic Typing in Python

Python is a dynamically typed language.

Meaning:

• You don’t need to declare a type
• Type can change at runtime

Example:

x = 10       # x is int
x = "Hello"  # now x is str

This is valid in Python.

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4️⃣ Variable Memory Concept

a = 10
b = 10

Both a and b will point to the same memory location because integers are immutable.

But:

a = 10
a = 20   # new object created

Value changes → New memory created.

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5️⃣ Types of Variables in Python

📌 Global Variable

Defined outside functions → can be used anywhere

x = 100  # global variable

def show():
    print(x)

show()

📌 Local Variable

Created inside a function → only works inside that function

def fun():
    y = 50   # local variable
    print(y)

fun()

📌 Changing Global Variable inside a function

You need global keyword:

x = 10

def modify():
    global x
    x = 20

modify()
print(x)   # 20

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6️⃣ Constants in Python

Python does not have true constants.
But by convention, we write constants in UPPERCASE.

PI = 3.14
GRAVITY = 9.8

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7️⃣ Deleting Variables

You can delete a variable using del:

x = 10
del x
print(x)   # error → variable deleted

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8️⃣ Input with Variables

name = input("Enter your name: ")
age = int(input("Enter age: "))

print("Your name is", name)
print("Your age is", age)

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9️⃣ Multiple Assignments - More Examples

✔ Swap two variables

a = 5
b = 10
a, b = b, a

print(a, b)   # 10 5

✔ Unpacking a list/tuple

numbers = [1, 2, 3]
a, b, c = numbers
print(a, b, c)

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🔟 Practice Questions

Try these for mastery 👇

⭐ Easy

1. Create a variable to store your name and print it.
2. Store two numbers in variables and print their sum.
3. Check the type of each variable:

   a = 10
   b = "Meenu"
   c = 5.5
   

⭐ Medium

4. Swap 3 variables without using a temporary variable.
5. Explain the difference between global and local variables with example.
6. Write a program that takes user input for three values and prints the largest.

⭐ Hard

7. Show how dynamic typing works with an example.
8. Demonstrate memory allocation using id() function.
9. Create a program that uses both local and global variables.

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If you want, I can also provide: 👉 Diagrams
👉 Notes for exam
👉 PDF version
👉 MCQs with answers
👉 Python variable exercises with solutions

Which one would you like next? 😊