Activity: Hello, World!

In this activity, you will run Python from the command line and become acquainted with its most basic mode of operation.

To get started, log onto the Rivanna shell and move into in the course directory you created for this class.

Which Python?

Once you are in Rivanna, you will want to know which version of Python you have installed as the default.

To find out, from the command line type:

which python

This will show you the “path” to a python interpreter. For example:

If you do not see “minifprge” in that path, then run the following command:

module load miniforge

This will update your environment to use Anaconda’s distribution of Python.

After running the command, enter the command to see which pythion is being used to confirm that it is the one from Ancaconda.

Note that you can use module to run other programs on your Rivanna account.

Type module list to see which programs have already been installed on your account.

Type module spider to see all the programs you can install.

From the command line, enter python

You should get the Python Shell:

This is also called the Python standard REPL, which stands for “Read-Eval-Print Loop”.

Make sure you see that you are using version 3 of Python.

If you see Python 2, exit the shell by entering quit() and try again by entering python3 at the command line.

At the >>> prompt type print("Hello, World!") and press return.

If you’ve never used Python, you’ve just completed an important ritual. If you have used Python, well, you did it again :-)

Now, enter following line at the prompt and press return:

import this

What do you see?

To exit the Python Shell, enter quit() or exit() and hit return.

Now create a file called hello.py using the command line editor nano and write print("Hello, World!").

Then press Ctrl-0 to save the file and Ctrl-X to exit the program.

Finally, run the program from the command line by directly invoking the Python interpreter python, like so:

python hello.py