Montreal Python Workshop/Friday/OSX Python scripts
We are going to practice writing and running Python scripts.
Start your text editor
- Launch the Smultron 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:
print "Hello World!"
- Save the script as
hello.py
in your home directory. The.py
extension indicates that this file contains Python code.
Run the script
- Start a command prompt. See the terminal navigation on OS X instructions for the steps to do this. Recall that a terminal prompt will look like
jesstess$
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 typeexit()
on a line by itself and then hit enter to exit Python and return to a terminal prompt. - Navigate to your home directory from a command prompt, using the
ls
,pwd
, andcd
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! - Once you are in your home directory, you'll see
hello.py
in the output ofls
. - Type
python hello.py
and hit 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 hit enter.
Success
You created and ran your first Python script!
- When you run the
python
command by itself, you start a Python prompt. You can execute Python code interactively at that prompt. - When you run the
python
command with a file name as an argument, Python executes the Python code in that file.