Hello World in Python

print() writes text to standard output followed by a newline. Unlike C++ or Go, there’s no boilerplate — no imports, no main() function, no semicolons. Python executes top-to-bottom from the first line.

Let’s pass a name in as a command-line argument using sys.argv.

sys.argv is a list where sys.argv[0] is the script name and sys.argv[1] is the first argument. Try running ./main Alice in the terminal — or just ./main to see the usage message.

f-strings (the f"..." syntax) let you embed expressions directly inside strings using {}.

Now let’s read input interactively from the user using input().

input() prints the prompt, then waits for the user to type something and press Enter. It always returns a string — use int() or float() to convert if you need a number.

Python’s type system is dynamic — variables don’t need type declarations. Let’s look at the basic types.

Python infers the type from the value you assign. type(x).__name__ returns the type name as a string — useful for debugging.

The :.2f format spec inside an f-string rounds floats to 2 decimal places.

Python also has excellent multi-line string support with triple quotes.

Triple-quoted strings ("""...""" or '''...''') span multiple lines without escape sequences. .upper() returns an uppercase copy — strings in Python have many useful built-in methods. .splitlines() splits on newlines and returns a list.

Finally, let’s look at file I/O — writing and reading a file.