Python Input and Output

Talking to the computer, both ways

Every useful program does two things: it shows information to a person, and it takes in information from a person. In Python, those two jobs belong to print() and input(). Together they are called output (what the program shows) and input (what the user types). Master these two functions and your programs stop being silent calculations — they start having conversations.

This lesson assumes you can run a Python program. If you have not yet, work through your first Python program first, then come back.

Output: the print() function

You have probably already met print(). It sends text to the screen:

print("Hello, world!")
print("Learning Python is fun.")

This produces two lines:

Hello, world!
Learning Python is fun.

But print() can do more than show one piece of text. You can pass it several values separated by commas, and it prints them all with a space between:

name = "Maya"
age = 12
print("Name:", name, "Age:", age)

Output:

Name: Maya Age: 12

Notice Python automatically put spaces between the items and turned the number 12 into text for you.

Controlling print with sep and end

Two special settings change how print() behaves: sep and end.

sep (separator) sets what goes between the values:

print("2024", "11", "30", sep="-")   # 2024-11-30
print("a", "b", "c", sep="")         # abc

end sets what is printed after everything, instead of starting a new line. By default it is a newline, which is why each print() lands on its own line. Change it to keep printing on the same line:

print("Loading", end="")
print("...", end="")
print("done!")

Output:

Loading...done!

All three prints share one line because the first two used end="" instead of a newline.

Input: the input() function

input() pauses your program, waits for the user to type a line and press Enter, then hands that text back to you:

name = input("What is your name? ")
print("Nice to meet you,", name)

When you run it, the program prints the prompt, stops, and blinks a cursor. If you type Sam and press Enter, you see:

What is your name? Sam
Nice to meet you, Sam

The text inside input("...") is the prompt — a message telling the user what to type. Always include a clear prompt so the user knows what is expected.

The golden rule: input() always returns a string

Here is the single most important fact in this whole lesson, and the source of countless beginner bugs:

input() always gives you back a string — text — even if the user types a number.

Watch what goes wrong:

age = input("How old are you? ")
print(age + 1)   # ERROR!

If you type 12, Python stores the text "12", not the number 12. Trying to add the number 1 to text causes a TypeError. You cannot add a number to a string.

Converting text to numbers with int() and float()

To do maths, you must convert the text into a number first:

• int(...) turns text into a whole number (integer).
• float(...) turns text into a decimal number.

age = int(input("How old are you? "))
print("Next year you will be", age + 1)

price = float(input("Enter a price: "))
print("With tax:", price * 1.2)

Now int(input(...)) reads the text and immediately converts it to a number, so the maths works. Use int() for whole numbers like age or count, and float() for decimals like price or weight.

One warning: int("hello") or int("3.5") will crash with a ValueError, because that text is not a whole number. For now, assume the user types sensibly; handling bad input neatly comes later.

f-strings: the clean way to build output

Joining text and variables with commas works, but f-strings are clearer and more powerful. An f-string starts with the letter f before the quote, and you drop variables straight into the text using curly braces {}:

name = "Maya"
age = 12
print(f"{name} is {age} years old.")

Output:

Maya is 12 years old.

The {name} and {age} are replaced by the variables' values. You can even put calculations inside the braces:

price = 8
print(f"Three items cost {price * 3} pounds.")   # Three items cost 24 pounds.

f-strings are the standard, readable way to build output in modern Python. To go deeper into shaping text, see working with text and strings.

Worked example: a simple greeting and age calculator

Let's combine everything into one small, complete program that talks to the user.

print("Welcome to the Age Machine!")

name = input("What is your name? ")
birth_year = int(input("What year were you born? "))

current_year = 2025
age = current_year - birth_year

print(f"Hello, {name}!")
print(f"In {current_year} you turn {age} years old.")
print(f"In ten years you will be {age + 10}.")

Step by step, here is what happens:

1. print("Welcome to the Age Machine!") shows a heading — pure output.
2. input("What is your name? ") pauses and reads the name as text. A name stays as a string, so no conversion is needed.
3. int(input("What year were you born? ")) reads the birth year and converts it to a whole number, because we will do maths with it.
4. current_year - birth_year calculates the age using two numbers.
5. The three f-string prints build clear sentences, dropping name, age and even the calculation age + 10 straight into the text.

If a user enters Maya and 2013, the output is:

Welcome to the Age Machine!
What is your name? Maya
What year were you born? 2013
Hello, Maya!
In 2025 you turn 12 years old.
In ten years you will be 22.

Try it yourself

Build a small program that has a real conversation with the user:

• Ask for the user's name and store it as text.
• Ask for the number of pets they have, converting it with int().
• Ask for the price of one item, converting it with float().
• Print a friendly summary using f-strings, for example: Maya has 2 pets, and 3 items cost 24.0 pounds.
• Experiment with sep and end on at least one print() to control its layout.

When your program reads input cleanly and prints clear output, you are ready to make it react to different answers. That is the job of conditionals — see conditionals in Python next.