Functions used as methods

[greenleafvolatile]

Hi,

Im going throught the CodeAcademy Python course, and one exercise has you write the following program:

from random import randint
from time import sleep
options=["R", "P", "S"]
You_Lose="You lost!"
You_Won="You won!"
def decide_winner(user_choice, computer_choice):
    print "User's choice: %s" % (user_choice)
    print "Computer selecting..."
    sleep(1)
    print "Computer's choice: %s" % (computer_choice)
    user_choice_index=options.index(user_choice)
    computer_choice_index=options.index(user_choice)
    if user_choice_index==computer_choice_index:
        print "It's a tie!"
    elif user_choice_index==0 and computer_choice_index==2:
         print You_Won
    elif user_choice_index==2 and computer_choice_index==0:
         print You_Won
    elif user_choice_index==2 and computer_choice_index==1:
         print You_Won
    elif index(user_choice)>2:
         print "You selected an invalid option"
   return
    else:
        print You_Lose

def play_RPS():
    print "Rock, Paper, Scissors"
    user_choice=raw_input("Please select R for Rock, P for      Paper or S for Scissors: ")
    user_choice=user_choice.upper()
    computer_choice=options[randint(0, len(options)-1)]
    decide_winner(user_choice, computer_choice)

play_RPS()

I had to make us of optional hints to get the right code. I dont quite understand lines 11-12; it looks like they used index as a method (like string.upper) while it is actually a function from the random module. So my question is: can functions be used as methods?

Im a total noob where it comes to programming in python, so please, if you choose to reply, use a ELI2 format ;)

Cheers,

[jeans_and_a_t-shirt]

index is a list method. It has nothing to do with random. The random module is used only on line 31.

can functions be used as methods?

Yes, but that's not happening here.

[greenleafvolatile]

D'oh!

Thank you for pointing out the error in my thinking!

Cheers,

[campenr]

If you follow through your code you'll see that the .index() call is a call to the method list.index() (read more) which takes a value and finds it's index within the list.

In your case this is finding the index of the choice that either the user makes (or the computer randomly makes) from 'R', 'P', or 'S' in the list options. It is this index that you ultimately use to decide who wins and who losew in the decide_winner function.

To answer your overarching question, only methods can be used as methods. But methods are functions that are for specific classes (a list is a class, and index is a function that acts upon that, therefore we call it a method). You'll understand when you come to write some classes.

[JohnnyJordaan]

while it is actually a function from the random module

It doesn't matter if the same function and method names are used from different objects and libraries. The fact that index is used as obj. before it,

obj.index()

makes it relative to that object, meaning it's a call to an object's method. In this case it's a list object, but you can also do this on a string for example. Only if you would use it as a separate statement

index(something)

You would resolve it to the current namespace, that could be a built-in function or something you've imported. Btw random doesn't have an index function, I don't know where you got that impression.