By this time you’ve probably typed and retyped a lot of code in the Python interactive interpreter. If you mess up when retyping a complex example, you have to enter it again. Using the arrow keys to access and modify previous commands is helpful but only goes so far. In this section, we see two important ways to reuse code: text editors and Python functions.
The Python interactive interpreter performs your instructions as soon as you type them. Often, it is better to compose a multiline program using a text editor, then ask Python to run the whole program at once. Using IDLE, you can do this by going to the File menu and opening a new window. Try this now, and enter the following one-line program:
print 'Monty Python'
Save this program in a file called monty.py, then go to the Run menu and select the command Run Module. (We’ll learn what modules are shortly.) The result in the main IDLE window should look like this:
>>> ================================ RESTART ================================ >>> Monty Python >>>
You can also type
from monty import
* and it will do the same thing.
From now on, you have a choice of using the interactive
interpreter or a text editor to create your programs. It is often
convenient to test your ideas using the interpreter, revising a line
of code until it does what you expect. Once you’re ready, you can
paste the code (minus any
... prompts) into the text editor, continue to expand it, ...