Master Python’s Interactive Interpreter and Run Your First Script

What is a REPL? Python’s shell is a Read‑Eval‑Print Loop that reads commands, evaluates them, prints the result, and repeats until you exit.

Starting the interpreter Open a terminal (Command Prompt or PowerShell on Windows; Terminal on macOS/Linux) and type python. If Python is correctly installed, the prompt >> appears.

Remember that Python is indentation‑sensitive. An extra space before print("Hello, World!") triggers an IndentationError:

>>   print("Hello, World!")
File "<stdin>", line 1
print("Hello, World!")
^
IndentationError: unexpected indent

When you’re finished, exit the REPL with exit() or quit().

Running a script from the command line For larger tasks, write a script file. Create hello.py with the single line: print("Hello, World!") Save the file, navigate to its directory in the terminal, and execute:

python hello.py

Python can run scripts without a .py extension, but using the standard extension improves readability.

Summary The interactive interpreter is handy for quick tests and learning, while scripts provide reusable, organized code for larger problems. Future articles will explore additional interpreter features and best practices.