To call our pv_f() function included in the Python program test01.py, we can use import test01 or from test01 import *. Obviously, it is more convenient to use pv_f() instead of test01.pv_f(). To call the function directly, we use from test01 import *. Refer to the following parallel structures:

>>>from math import *
>>>sqrt(3.5)
1.8708286933869707
>>>from test01 import * 
>>>pv_f(100,0.1,2)
82.64462809917354

When we are sure about the existence of a specific function in test01.py, we can import it specifically as follows:

>>>from math import ceil,sqrt,pi
>>>from test01 import pv_f

The del() built-in function is used to remove a function or variable, as shown in the following code:

>>>del pv_f
>>>dir()
['__builtins__', '__doc__', '__loader__', '__name__', 
'__package__']