Running scripts

So far, you've interacted with Python one line at a time in the REPL. For the rest of this session, we're going to write and execute longer programs.

Three ways of running scripts

Fundamentally, Python programs are just text files. You can write them in a text editor like Sublime and pass them to Python, which will execute them one line at a time. Here are three ways to run your Python programs. All work equally well, so choosing one is a matter of preference. Pick one method and stick to it for now.

Command line method

Open your text editor of choice (such as Sublime) and create a new file with this line:

print("Hello world!")

Save it with the name hello.py to a known location, such as your desktop. Open your terminal and move to the desktop directory:

$ cd Desktop

Once you're in the folder with your hello.py file, run it with:

$ python hello.py
Hello world!

As above, you should see the text Hello world! appear as output.

IPython Notebook

IPython Notebooks are graphical interfaces to Python that run in the browser. To start a notebook, enter

$ ipython notebook

in your terminal. You should see messages appear in your terminal window, and your browser should open to a list of files. Once IPython is open in the browser, click New in the top right and select Python under Notebook from the dropdown menu.

THe IPython interface consists of cells, which can contain text or Python code. In the first cell (the blank space next to the text that says In [ ], enter the text

print("Hello world!")

then hit Shift-Enter. You should see the output Hello world! appear below.

IDE

An IDE (Integrated Development Environment) is a program that can be used for both writing and running programs, and they usually come with a number of specialized features. Python comes with its own IDE, but it only runs well on Windows and Linux, not on OSX. More powerful cross-platform IDEs for Python exist, such as PyCharm and Spyder will also allow you to write and run Python programs on your desktop. Check out these tutorials if you're interested in using an IDE to write and execute Python code:

IDLE tutorial (not recommended fo OSX)

PyCharm Quickstart

Spyder tutorial