OSX Python scripts

We are going to practice writing and running Python programs (often called "scripts").

Start your text editor

 * 1) Launch the TextWrangler text editor. See the OS X text editor setup instructions for the steps to do this.
 * 2) Start a new, blank text file.

Write and save a short Python script

 * 1) Add the following line to your new text file:

print("Hello World!")


 * 1) Save the script as   in your home directory. The   extension indicates that this file contains Python code.

Run the script

 * 1) 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   on a line by itself and then press enter to exit Python and return to a terminal prompt.
 * 2) Navigate to your home directory from a terminal prompt, using the ,  , and   commands. 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!
 * 3) Once you are in your home directory, you'll see   in the output of.
 * 4) Type

python hello.py

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

print("Hello World!")

at a Python prompt and press enter.

Success
You created and ran your first Python script!


 * When you run the  command by itself, you start a Python prompt. You can execute Python code interactively at that prompt.
 * When you run the  command with a file name as an argument, Python executes the Python code in that file.