1.8. The Interactive Shell

Now that you have Python installed, what's this interactive shell thing you're running?

It's like this: Python leads a double life. It's an interpreter for scripts that you can run from the command line or run like applications, by double-clicking the scripts. But it's also an interactive shell that can evaluate arbitrary statements and expressions. This is extremely useful for debugging, quick hacking, and testing. I even know some people who use the Python interactive shell in lieu of a calculator!

Launch the Python interactive shell in whatever way works on your platform, and let's dive in with the steps shown here:

Example 1.5. First Steps in the Interactive Shell

>>> 1 + 1               1
>>> print 'hello world' 2
hello world
>>> x = 1               3
>>> y = 2
>>> x + y
1 The Python interactive shell can evaluate arbitrary Python expressions, including any basic arithmetic expression.
2 The interactive shell can execute arbitrary Python statements, including the print statement.
3 You can also assign values to variables, and the values will be remembered as long as the shell is open (but not any longer than that).