Your First Python Program (Line by Line)

Here is your first Python program. Three lines, and it does something real.

name = input("What is your name? ")
year = int(input("What year were you born? "))
print(f"Hi {name}, you are about {2026 - year} years old.")

The rest of this guide explains every part of it and shows you how to run it.

Step 1: create the file#

Make a folder called python-practice. Inside it, create a file named greet.py. The .py ending is what marks it as Python.

Any text editor works. VS Code is the usual choice — see VS Code setup for beginners. Do not use a word processor; it adds formatting that breaks code.

Step 2: type the program#

print("Hello, world!")

Type it rather than pasting it. Typing is where the muscle memory comes from.

Step 3: run it#

Open a terminal in that folder and run:

python greet.py

On macOS or Linux, use python3 greet.py. If neither is found, see how to install Python.

Making it interactive#

Now replace the file’s contents:

name = input("What is your name? ")
print("Hello, " + name + "!")

Line by line:

• input("What is your name? ") shows the question and waits for the person to type and press Enter.
• name = stores whatever they typed under the name name. See variables explained.
• print(...) displays the result. The + joins pieces of text together.

A nicer way to build text: f-strings#

Joining with + gets ugly fast. Put an f before the quotes and use braces instead:

name = "Ada"
age = 36
print(f"{name} is {age} years old.")

You can even do arithmetic inside the braces: f"Next year: {age + 1}".

The finished program#

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

age = 2026 - year

print(f"Hi {name}, you are about {age} years old.")

if age >= 18:
    print("You can vote.")
else:
    print(f"You can vote in {18 - age} years.")

That uses input, conversion, a variable, arithmetic, an f-string and a condition — the core of the language in nine lines.

Comments#

Anything after a # is ignored by Python and written for humans.

# Ask the user for their details
name = input("Name: ")   # this part runs

Use comments to explain why something is done, not what. The code already says what.

Where to go next#

• Python variables explained
• Python data types explained
• Build a number guessing game