Trying to set a variable from a value in a dictionary

Question

I'm learning python and am creating a rock paper scissors game.

I'm stuck on one part.

I have 4 variables currently (Although I would like to get it down to 2)

• pKey
• pChoice
• comKey
• comChoice

They look up the the Key and Value respectively in a dictionary.

choice = {1:'rock',  2:'paper',  3:'scissors'}

The problem I'm having is getting the keys from the dictionary using the variables.

Here's the code snippet that's giving me trouble

    print('--- 1 = Rock    2 = Paper     3 = Scissors --- ')
    pKey = input() # this is sets the key to the dictionary called choice
    while turn == 1: # this is the loop to make sure the player makes a valid choice
        if pKey == 1 or 2 or 3:
            pChoice = choice.values(pKey)  # this calls the value from choice dict and pKey variable
            break
        else:
            print('Please only user the numbers 1, 2 or 3 to choose')

    comKey = random.randint(1, 3)  # this sets the computer choices
    comChoice = choice.values(comKey)

Specifically the troublesome part is

 pChoice = choice.values(pKey)

and

 comChoice = choice.values(comKey)

I've tried everything I know from using brackets, trying different methods, and using different formats.

Would love to learn this! Thanks!

Answer 1

Sounds like you're just trying to do a dictionary lookup

pKey = 1
pChoice = choices[pKey]  # rock

dict.values is used to create a list (actually a dict_values object) with all the values of the dictionary. It's not used as a lookup.

---

As far as your code structure goes, it could use some work. The rock/paper/scissors choice is perfect for an Enum, but that might be a bit beyond you right now. Let's just try as a toplevel module constant.

ROCK = "rock"
PAPER = "paper"
SCISSORS = "scissors"

def get_choice():
    """get_choice asks the user to choose rock, paper, or scissors and
    returns their selection (or None if the input is wrong).
    """
    selection = input("1. Rock\n2. Paper\n3. Scissors\n>> ")
    return {"1": ROCK, "2": PAPER, "3": SCISSORS}.get(selection)

Addressing them as constants makes sure they're the same everywhere in your code, or else you get a very clear NameError (instead of an if branch not executing because you did if comChoice == "scisors")

---

A minimal example with an enum looks like:

from enum import Enum

Choices = Enum("Choices", "rock paper scissors")

def get_choice():
    selection = input(...)  # as above
    try:
        return Choices(int(selection))
    except ValueError:
        # user entered the wrong value
        return None

You could extend this by using the more verbose definition of the Enum and teach each Choice instance how to calculate the winner:

class Choices(Enum):
    rock = ("paper", "scissors")
    paper = ("scissors", "rock")
    scissors = ("rock", "paper")

    def __init__(self, loses, beats):
        self._loses = loses
        self._beats = beats

    @property
    def loses(self):
        return self.__class__[self._loses]

    @property
    def beats(self):
        return self.__class__[self._beats]

    def wins_against(self, other):
        return {self: 0, self.beats: 1, self.loses: -1}[other]

s, p, r = Choices["scissors"], Choices["paper"], Choices["rock"]
s.wins_against(p)  # 1
s.wins_against(s)  # 0
s.wins_against(r)  # -1

Unfortunately there's no great way to lose the abstraction in that (abstracting out "paper" to Choices.paper every time it's called) since you don't know what Choices["paper"] is when Choices.rock gets instantiated.