Error messages

Assuming that we issue the sqrt(3) command to estimate the square root of three, we would get the following error message:

>>>sqrt(3)
Traceback (most recent call last):
  File "<pyshell#17>", line 1, in <module>
    sqrt(3)
NameError: name 'sqrt' is not defined

The last line of the error message tells us that the sqrt() function is not defined. Later in the chapter, we learn that the sqrt() function is included in a module called math and that we have to load (import) the module before we can call the functions contained in it. A module is a package that contains a set of functions around a specific subject.

Can't call a variable without assignment

Assuming that we never assign a value to the abcde variable, after typing abcde, we would get the following error message:

>>>abcde
Traceback (most recent call last):
  File "<pyshell#0>", line 1, in <module>
    abcde
NameError: name 'abcde' is not defined
>>>

The last line tells...