Input & Output

Get user input and display results

User Input — Making Your Program Interactive

What Is It?

So far your programs just run — they don't ask the user for anything. With input(), your program can talk back and forth with the person using it. This is what makes programs interactive instead of one-way.

Syntax

python

name = input("What's your name? ")
print(f"Hello, {name}!")

Part	What it does
`input("prompt")`	Displays the prompt, waits for the user to type and press Enter
The return value	Whatever the user typed — always as a string
`name = ...`	Stores the user's response in the variable

How It Works

python

age = input("How old are you? ")
print(f"Next year you'll be {int(age) + 1}")

Step by step:

**Line 1**: `"How old are you? "` appears on screen. Program **pauses** and waits

User types `"25"` and presses Enter

Python stores `"25"` (as a *string*) in `age`

**Line 2**: `int(age)` converts it to the number `25`, adds `1`, and uses f-string to display

️ **Critical:** `input()` always returns a **string**, even if the user types a number. Convert with `int()` or `float()` before doing math!

Getting Multiple Inputs

python

name = input("Enter your name: ")
age = int(input("Enter your age: "))   # Convert right away
city = input("Enter your city: ")

print(f"{name} is {age} years old and lives in {city}.")

Why Use Input?

Without input, every program runs identically every time. Input makes programs dynamic:

**User profiles** — ask for name, preferences, settings

**Calculators** — ask what numbers to use

**Games** — guess the number, choose your move

**Forms & surveys** — collect and process responses

**CLI tools** — ask for file paths, options, confirmation

Common Mistakes

❌ Wrong	Why	✅ Right
`age = input("Age? ")` then `age + 1`	`age` is a string! Can't add number	`int(age) + 1`
`input("Enter number:")` without space after `:`	Prompt runs right into user's typing — looks messy	Use a space: `": "`
`int(input("Age? "))` with no error handling	Crashes if user types "twenty"	(Advanced) Use try/except
Forgetting to store the result	`input("Name: ")` alone runs but the input is lost!	Always assign: `name = input(...)`

Your Turn!

Write a program that:

Asks for the user's name

Asks for their favorite number

Prints: `"Hello {name}! Your number doubled is {number * 2}!"`

� **Hint:** Remember to convert the number with `int()` before doubling it!

💡Need a hint? (3 available)

#1input() always returns a string — convert with int() for math

#2Store the result in a variable

#3Use f-strings for clean output

🔑Show solution (try it yourself first!)

name = input("Enter your name: ")
num = int(input("Enter your favorite number: "))
print(f"Hello {name}! Your number doubled is {num * 2}!")

✏️ Code Editor

Loading Python...

📤 Output

Write your solution and click "Run Code" to test it!

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