Checking the existence of our functions

Again, we can use the dir() function to detect the existence of our just covered pv_f() function, as shown in the following code:

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

To save our file, we need to perform the following simple steps:

1. Navigate to File | New Window Ctrl + N and type the following two-liner code. A careful user would notice that after pressing the Enter key at the end of the first line, the second line will be indented automatically. While writing just two lines of code, it is not obvious. However, for a block of code with multiple lines, a correct indentation is critical. Later in the chapter, we will show and discuss this issue in more detail:

   def pv_f(fv,r,n):
       return fv/(1+r)**n
   

2. Click on File and then save (Ctrl + S) to save the preceding two lines of code. Assume that we name the file as test01.py. The default directory is Python33 in C:...