We are going to practice writing and running Python programs (often called "scripts").
Start your text editor
- Launch the TextWrangler text editor. See the OS X text editor setup instructions for the steps to do this.
- Start a new, blank text file.
Write and save a short Python script
- Add the following line to your new text file:
- Save the script as
hello.pyin your home directory. The
.pyextension indicates that this file contains Python code.
Run the script
- Start a terminal prompt. See the terminal navigation on OS X instructions for the steps to do this. Recall that a terminal prompt will look like
$and a Python prompt will look like
>>>. Make sure you are at a terminal prompt and not a Python prompt; if you are at a Python prompt, you can type
exit()on a line by itself and then press enter to exit Python and return to a terminal prompt.
- Navigate to your home directory from a terminal prompt, using the
cdcommands. See the terminal navigation on OS X instructions for a refresher on using these commands. Don't hesitate to get help from a staff member on this step if you need it -- it's a new way of navigating your computer, so it may be unintuitive at first!
- Once you are in your home directory, you'll see
hello.pyin the output of
and press enter. Doing this will cause Python to execute the contents of that script -- it should print "Hello World!" to the screen. What you've done here is run the Python application with an argument -- the name of a file, in this case "hello.py". Python knows that when you give it a file name as an argument, it should execute the contents of the provided file. You get the same result as if you typed
at a Python prompt and press enter.
You created and ran your first Python script!
- When you run the
pythoncommand by itself, you start a Python prompt. You can execute Python code interactively at that prompt.
- When you run the
pythoncommand with a file name as an argument, Python executes the Python code in that file.