Python by Example

Hello World

The smallest runnable Python program - printing a message and understanding the script guard pattern.

The smallest runnable Python program prints a message to the console. Run it with python file.py, or add a shebang line (#!/usr/bin/env python3) to make the file executable directly. The if __name__ == "__main__": guard lets the same file act as both a runnable script and an importable module.

print() writes its argument to stdout, followed by a newline. This is how Python says hello to the world.

print("Hello, World!")

Running the script produces:

OUTPUT
Hello, World!

Wrapping your script logic inside if __name__ == "__main__": lets the file be imported by another module without running the script body. __name__ is the module's name when imported, or "__main__" when run directly.

def greet(name):
    print(f"Hello, {name}!")
 
if __name__ == "__main__":
    greet("World")

In production

print() is fine for scripts and CLIs. Production services need the stdlib logging module (or structlog) so log levels, structured fields, and request-correlation IDs survive into Datadog or Loki. Plain print() writes to stdout with no level metadata and cannot be silenced without code changes.

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