Hello World! Your first program
In this lesson, we will start using the console to write in Python.
As with all programming languages, it is now a good practice to start by writing the writing Hello World!
If you have not already done so, download the latest Python 3.x version from www.python.org, suitable for your operating system. Once installed, you will be able to access the console in several ways:
- through the command line, starting the interpreter directly
- as part of the IDLE, the GUI that is installed together with the basic Python installation
In both cases, the interpreter will wait for your commands with a prompt consisting of three arrows
Write your first command
>>>print( ‘Hello World!)
then press enter. From the console you will see the text “Hello World” appear directly under the command.
The Python console
The Python console is a program that allows you to enter Python commands one line at a time. This is called REPL (Read-Eval-Print-Loop).
Once you have finished working with the console you can close the Python session by writing the command quit () or exit () and then pressing ENTER.
However, there are commands that will allow you to close both the console and the programs running abruptly.
CTRL + Z to stop the console from running
CTRL + C to stop running a program in Python
The second command will be very useful in cases where a program in Python will loop or it will take too long to wait for the result. With CTRL + C you can abruptly interrupt the program and double check the code to see what caused the loop.