Input, Output & Comments

2. f-strings

2.1 What are f-strings?
1. Imagine a form letter with blanks: Dear ___, your order of ___ will arrive on ___. If we have values stored in variables, f-strings help us fill those blanks automatically. Example name = "Ram" item = "book" date = "Monday"print(f"Dear {name}, your order of {item} will arrive on {date}.")Output: Dear Ram, your order of book will arrive on Monday. f-strings are used to create formatted output by placing variables or expressions directly inside a string. Syntax:f"Text {variable}" 📌 We must write f before the string. 📌 Variables or expressions are written inside curly braces { }.

2.2 Why use f-strings?
1. Without f-string: name = "Rabindra" age = 30print("My name is", name, "and I am", age, "years old.")Output: My name is Rabindra and I am 30 years old. Using f-string: print(f"My name is {name} and I am {age} years old.")Output: My name is Rabindra and I am 30 years old. ✅ f-strings make the output cleaner and easier to understand.
2.3 Using Expressions inside f-strings
1. We can also write expressions inside curly braces. Example: age = 30 print(f"Next year, I will be {age + 1} years old.")Output: Next year, I will be 31 years old.

3. Format Specifiers

3.1 What are Format Specifiers?
1. A format specifier is a short instruction that tells Python exactly how we want a value to look. It is similar to choosing formatting options in Word, such as alignment, spacing, or decimal places. Format specifiers are used inside f-strings to customize output. They help us control: 📏 Width 🎯 Decimal places ↔️ Alignment ✨ Padding characters Syntax:f"{variable:format_specifier}"
3.2 🎯 Decimal Formatting
1. We can control the number of digits after decimal point. Example: num = 3.14159 print(f"{num:.2f}")Output: 3.14 Here, .2f means display the number with 2 digits after decimal point.
3.3 📏 Width Formatting
1. Width means the minimum space given to display a value. Example: num = 123 print(f"{num:10}")Output: 123 Here, width 10 means Python uses 10 spaces to display the value.
3.4 ↔️ Alignment
1. We can align values using: < ➜ Left align > ➜ Right align ^ ➜ Center align Example: item = "Apple"print(f"{item:<10}") # Left aligned print(f"{item:>10}") # Right aligned print(f"{item:^10}") # Center aligned

3.5 ✨ Fill Character
1. We can fill empty spaces with a character. Example: num = 123print(f"{num:->10}") # ➜ -------123 print(f"{num:-<10}") # ➜ 123------- print(f"{num:#^11}") # ➜ ####123####
3.6 Format Specifier Breakdown
1. Example: print(f"{num:->10}") Here: - ➜ Fill character > ➜ Right alignment 10 ➜ Width Example: print(f"{num:.2f}") Here: .2 ➜ Two digits after decimal f ➜ Floating-point number

3.7 Table-like Output Example
1. item_1 = "Apple" price_1 = 3item_2 = "Banana" price_2 = 10item_3 = "Orange" price_3 = 200print(f"{'Item':<12}{'Price':>5}") print("-" * 17) print(f"{item_1:<12}{price_1:>5}") print(f"{item_2:<12}{price_2:>5}") print(f"{item_3:<12}{price_3:>5}")Output: Item Price ----------------- Apple 3 Banana 10 Orange 200

4. User Input

4.1 ⌨️ What is input()?
1. input() is used to take input from the user. Example: name = input("Enter your name: ") print(f"Hello, {name}!") If user enters Rabindra, output will be: Hello, Rabindra!
4.2 ⌨️ input() Always Returns String
1. input() always returns data as a string. Example: num_1 = input("Enter first number: ") num_2 = input("Enter second number: ")print(num_1 + num_2) If user enters: 10 5 Output: 105 😕 Why did Python show 105 instead of 15? This happened because input() returns values as strings. So Python joined "10" and "5" as text.

4.3 ⌨️ Type Conversion with input()
1. To perform mathematical operations, we need to convert input into number. Example: num_1 = int(input("Enter first number: ")) num_2 = int(input("Enter second number: "))total = num_1 + num_2 print(f"Sum = {total}") If user enters: 10 5 Output: Sum = 15
4.4 ⌨️ Taking Float Input
1. If the input can contain decimal value, use float(). Example: price = float(input("Enter price: ")) print(f"Price = Rs. {price:.2f}")
4.5 ⌨️ Input and Calculation Example
1. length_in_cm = float(input("Enter length in cm: ")) length_in_m = length_in_cm / 100 print(f"Length = {length_in_m:.2f} m")

5. Comments

5.1 What are Comments?
1. Comments are notes written inside code. They are not executed by Python. Comments are used to: 📝 Explain code 📌 Improve readability 🧠 Help us remember logic
5.2 Single-line Comments
1. Single-line comments start with #. Example: # This program displays a greeting messagename = "Rabindra" print(f"Hello, {name}!")
5.3 Inline Comments
1. Comments can also be written beside code. Example: age = 30 # stores age of user print(age)
5.4 Block Notes using Triple Quotes
1. Python does not have a separate multi-line comment symbol like some other languages. However, triple quotes can be used to write multi-line notes when they are not assigned to a variable. Example: """ This program takes user information and displays it in a formatted way. """name = "Rabindra" print(name) 📌 Triple quotes actually create multi-line strings, but beginners often use them as block notes.
5.5 Comment Shortcut in VS Code
1. In VS Code, we can use: Ctrl + / to comment or uncomment selected lines.