Why does the return statement not return any text, whilst print does?

Question

when i run

profitable_gamble(0.2, 50, 9)

with this function there is no output

def profitable_gamble(prob, prize, pay):
    if prob * prize > pay:
        return "true"
    else:
        return "false"

however when i change the function to use print()

def profitable_gamble(prob, prize, pay):
    if prob * prize > pay:
        print("true")
    else:
        print("false")

I get "true" as expected. how can I get this to happen while using return rather than print?

Answer 1

This is what you think your code should do:

def profitable_gamble(prob, prize, pay):
    if prob * prize > pay:
        return "true"
    else:
        return "false"


returned_value = profitable_gamble(0.2, 50, 9)
print(returned_value)

But then you never tell it to print anything, so it doesn't. If you only call this:

profitable_gamble(0.2, 50, 9)

Then your function returns "true" or "false" nonetheless.... you just never do anything with it, so it just goes to die in the call stack.

EDIT: you may also be confused because of the use of command-line (or something like Ipython notebooks). In those interactive shells, if you do:

profitable_gamble(0.2, 50, 9)
>> "true"

Then indeed it does show the value on screen. However, this is just because you're using a shell which (presumably) outputs the result of the call to the console for you. So essentially that shell (be it a terminal or some interactive notebook) does for you the additional print() statement....

As a note - there is little reason in general to do something like

return "true"

In python. Generally you would want to just use the boolean:

return True

(notice the capital T).

Especially since you can anyway do print(some_boolean_variable) or str(some_boolean_variable).... The added benefits being that it's much easier to test a boolean value than to compare the string "true" everytime...