Remember import this from the first exercise in this course? That was an example of import*ing a *module. A module is a file that contains definitions—including variables and functions—that you can use once it is imported.
Before we try any fancy importing, let’s see what Python already knows about square roots. On line 3 in the editor, ask Python to
print sqrt(25)which we would expect to equal five.
Instead, it throws an error.