Variables & Data Types

• ✨ Python variables spring into existence when you assign them. and can change type at runtime. ✅
• 🔁 Python variables are created when you are first assigned a value — they reference objects and Python is dynamically typed, so a name can refer to different types over time. ♻️
• 🧭 Use clear, descriptive names (snake_case by convention), do not start identifiers with digits, and avoid reserved keywords. 🚫
• 🔍 Use type(value) to inspect a value’s type.
• You can assign multiple variables in one line (e.g., x, y = 1, 2). By convention, constants are written in ALL_CAPS. 📣

quantity = 12       # int
unit_price = 50.00   # float
fruit = "Apple"     # string
in_stock = True     # bool

Screenshot of Python code showing variable assignments and printing their types.

Complete Code :

quantity = 12       # int
unit_price = 50.00   # float
fruit = "Apple"     # string
in_stock = True     # bool

print(type(quantity))   # <class 'int'>
print(type(unit_price)) # <class 'float'>
print(type(fruit))      # <class 'str'>
print(type(in_stock))   # <class 'bool'>

📌 Let’s compare it with other programming languages.

Variable Declaration in Other Languages

In C# and JavaScript you must declare a type or use let/const:

C# Example:

int count = 1;
string name = "Banky";

JavaScript Example:

let count = 1;
const name = "Banky";

🔠 Naming Conventions Comparison

👉 Click to expand: Comparison of common naming conventions

Using the example: “maximum retry count”

Convention	Example	Typical Usage
snake_case	max_retry_count	Variables, functions (Python, Ruby)
camelCase	maxRetryCount	Variables, methods (JS, C#, Java)
PascalCase	MaxRetryCount	Classes, enums, types
ALL_CAPS	MAX_RETRY_COUNT	Constants, environment variables

🔑 Key takeaway:
Naming conventions are not cosmetic — they communicate intent to other developers.

Quick Quiz: Python Variables

1. How do you create a string in Python?

   name := “Ada” name = “Ada” string name = “Ada” let name = “Ada”
   Correct: name = “Ada”

2. Which of these is a valid Python variable name?

   2nd-value total-cost total_cost total cost
   Correct: total_cost

3. What built-in function shows a variable’s type?

   typeof() inspect() type() class()
   Correct: type()

4. What happens when you reassign x = 1 to x = “one” in Python?

   Raises a type error Makes x immutable x now references a string Requires redeclaring x
   Correct: x now references a string

5. How do you assign multiple variables in one line?

   x = 1; y x, y = 1, 2 set(x, y, 1, 2) declare x=1, y=2
   Correct: x, y = 1, 2

6. By convention, how do you name constants in Python?

   camelCase PascalCase snake_case ALL_CAPS
   Correct: ALL_CAPS

7. What’s the Pythonic way to swap two variables?

   tmp = a; a = b; b = tmp a, b = b, a swap(a, b) a == b
   Correct: a, b = b, a

8. Which assignment would raise a SyntaxError?

   1value = 5 value_1 = 5 value1 = 5 value_1_5 = 5
   Correct: 1value = 5

9. Which is the correct boolean literal in Python?

   TRUE True true yes
   Correct: True

10. How do you create a multiline string?

    Using triple quotes: """Hello""" Multiline(“Hello”) string.multiline(“Hello”) < Hello >
    Correct: Using triple quotes

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