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               
2
>>> print 'hello world' 
hello world
>>> x = 1               
>>> y = 2
>>> x + y
3

	The Python interactive shell can evaluate arbitrary Python expressions, including any basic arithmetic expression.
	The interactive shell can execute arbitrary Python statements, including the print statement.
	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).