Python basics - Day 04

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Day 4 – Input & Output

Project: Create an “Interactive Greeting App”

01. Learning Goal

By the end of this lesson, you will be able to:

Display information using print()
Receive user input using input()
Format messages neatly with f-strings
Build an interactive console program

02. Problem Scenario

You are creating a small interactive app that asks for the user’s name and age,

then prints a personalized greeting with properly formatted text and numbers.

03. Step 1 – Output with print()

The print() function displays text or variable values on screen.

You can separate multiple values with commas — Python will add spaces automatically.

print("Hello!")
print("Age:", 25, "years old")
# Output: Age: 25 years old

04. Step 2 – Input with input()

The input() function reads user input as a string (str).
Use a prompt message to ask the user for data.

name = input("Enter your name: ")
print("Hello,", name)

Note: Input values are always strings, so convert them with int() if you need numbers.

age = int(input("Enter your age: "))
print("Next year, you’ll be", age + 1)

05. Step 3 – Using f-strings (Formatted Strings)

An f-string allows you to insert variables directly into strings.
Just prefix the string with f and use {} to include variables.

name = "Sabin"
age = 25
print(f"My name is {name}, and I am {age} years old.")

You can also format numbers easily:

pi = 3.141592
print(f"Pi is approximately {pi:.2f}")   # 3.14

06. Step 4 – Multi-line Output

To print multiple lines at once, use triple quotes (""" """ or ''' ''').

msg = """Starting Python study!
Today we learn about input and output.
"""
print(msg)

07. Step 5 – Practice Examples

Example 1: Input + Output

food = input("What’s your favorite food? ")
print("Your favorite food is", food, "!")

Example 2: f-string Practice

name = input("Enter your name: ")
age = int(input("Enter your age: "))
print(f"{name}, you are {age} years old. Next year, you'll be {age + 1}!")

Example 3: Floating-point Output

num = 3.14159
print(f"One decimal place: {num:.1f}")
print(f"Three decimal places: {num:.3f}")

08. Step 6 – Mini Project: Interactive Greeting App

Now combine everything to create your own interactive greeting program.

name = input("What is your name? ")
age = int(input("How old are you? "))
print(f"Nice to meet you, {name}!")
print(f"Next year, you’ll be {age + 1} years old.")