🐍 Lesson 12: Python Input & Output – Interact with Users

Welcome to Lesson 12! Today we’ll learn how to take input from users and display output in Python. These are essential skills for making interactive programs.

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⭐ What You Will Learn in This Lesson

• Display messages and values using print()
• Take user input with input()
• Convert input to numbers for calculations
• Format output neatly using concatenation, commas, and f-strings
• Create interactive programs

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👥 Who Is This Lesson For?

• Beginners learning Python programming
• Students building interactive scripts or small projects
• Anyone who wants to understand user input/output in Python

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📦 1. Displaying Output with print()

# Print text
print("Hello, Python!")

# Print multiple items
name = "Alice"
age = 25
print("Name:", name, "Age:", age)

# Using f-strings (Python 3.6+)
print(f"My name is {name} and I am {age} years old.")

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🧩 2. Taking Input with input()

# Ask user for their name
name = input("Enter your name: ")
print("Hello, " + name + "!")

# Ask user for a number
num = input("Enter a number: ")
print("You entered:", num)

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⚠ Important Note

The input() function always returns a string. To perform math, you must convert it to an integer or float:

num = int(input("Enter an integer: "))
print(num + 5)

price = float(input("Enter a price: "))
print(price * 2)

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🧩 3. Formatting Output

• Concatenate using +
• Comma separation in print()
• Use f-strings for cleaner formatting

name = "Bob"
score = 95

print("Student " + name + " scored " + str(score))
print(f"Student {name} scored {score}")

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🧩 4. Why Input & Output Matter

• Make programs interactive
• Take user data for calculations
• Display results clearly
• Essential for projects, games, and apps

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🧪 Practice

1. Ask the user for their favorite color and print it in a sentence.
2. Take two numbers from the user and print their sum.
3. Ask for the radius of a circle and print its area.
4. Use f-strings to display your name and age in a sentence.
5. Take a number input and print its square and cube.

Bonus: Experiment with different ways of formatting output using f-strings, including limiting decimal places for numbers.

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❌ Common Mistakes

• Forgetting that input() always returns a string
• Not converting string input to int or float for calculations
• Misusing concatenation vs commas vs f-strings

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❓ Frequently Asked Questions (FAQ)

1. How do I take numbers as input?

Use int() or float() to convert string input to numbers.

2. Can I combine input() and print() in one line?

Yes. For example: print("Hello, " + input("Enter your name: "))

3. Are f-strings better than concatenation?

Yes. f-strings are cleaner, easier to read, and less error-prone.

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🚀 What’s Next?

In the next lesson, you’ll learn about:

• Handling errors and exceptions in Python
• Making your programs more robust
• Using try, except, and finally

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➡ Next Lesson

Go to Lesson 13 →