Function 正确定义并正常工作，但未在终端中打印结果

Question

I recently wrote a simple function that gets the present value of an asset, the function PV works properly and I have tested it. The function prints well in my pv file. However, when I run this code in the main file it does not print the output to the terminal and just closes after taking the inputs. Is there a reason for this? For reference the functions just perform some simple mathematics problems.

Below is a minimal reproduction, both files are in the same folder. in file_x you have a function that works like this:

def func(w,x,y,z):
    z1 = w/(1 + (x/100))**(y*z)
    print(z1)
    return 0

this function is then imported into another file which is written like so

from file_x import func

w = int(input("Future Value: "))
x = float(input("ROR: "))
y = float(input("# of periods: "))
z = float(input("# of payment per anum: "))

func(w,x,y,z)

My problem is that when I run the 2nd file it takes the inputs properly but does not print the result from the function. Hope it was explained properly

Answer 1

In interactive mode an unused expression (here PV(w,x,y,z) which does returns a value and that value is not used) is printed to the terminal, because it is a common way to just display expression values.

But when you run a script in a non interactive mode ( python script.py ) then those unused expression are just discarded. As a general rule, you should never have such an unused expression in a script, because the behaviour will depend on the interactive mode of the interpretor.

So you should be explicit:

_ = PV(w,x,y,z)     # value will be discarded even in interactive mode

or

print(PV(w,x,y,z))  # value will be printed even in non interactive mode