Re: [Tutor] more rps

[Alan Gauld]

Let me start by saying that your code is pretty

much OK as is. Indeed even using clssses for an

RPS game is probably overkill to some extent.

 

What follows should be seen more as some ideas

for experimentation and building towards a more

flexible/expandable architecture for future

projects. Its really about introducing some

alternative approaches and increasing consistency.

It is definitely not "better" - and indeed could

definitely be improved in several ways.

 

> class Human:
>   def __init__(self):
>     self.points = 0
>     self.choice = " "
>
>   def plays(self):
>     fromUser = raw_input("Pick (R)ock, (P)aper, or
>               (S)cissors! ")
>     translate = {'r':'rock', 's':'scissors',
>               'p':'paper'}
>     try:
>        self.choice = translate[fromUser.lower()]
>     except KeyError:
>        print 'Invalid Response'
>
> class Computer:
>    def __init__(self):
>      self.points = 0
>      self.choice = " "
>
>   def plays(self):
>     comp_choice = random.randint(0,2)
>     if comp_choice == 0:
>        self.choice = 'rock'
>     elif comp_choice == 1:
>        self.choice = 'paper'
>     else:
>       self.choice = 'scissors'

While its of little real advantage for this program 

I'd be tempted to introduce a Player superclass to avoid

code duplication. The protocol of both classes

here is the same and they both pass the "is-a"

test for inheritance - ie. they are both Players.

 

class Player:

   def __init__(self):

     self.points = 0
     self.choice = " "

 

   def getChoice(self): pass   # implemented in subclass

   def plays(self):

     choice = self.getChoice()
     if choice == 0:
        self.choice = 'rock'
     elif choice == 1:
        self.choice = 'paper'
     else:
       self.choice = 'scissors'

Notice I put the plays function in the Player class.

By unifying the representation of choice we can use

that function for both and just implement a

relatively simple getChoice method in each subclass

and we are done... (In fact we could simplify still

further by storing the choice in its numeric form

and using a class level dictionary to translate

that to a string for printing - although in fact

you never print what the choices were - maybe you

should?)

 

 

class Human(Player):

   def getChoice(self):

      choice = raw_input('Choice - rps: ').lower()

      if choice in 'rps':

         return {'r':0,'p':1,'s':2}[choice]

      else: raise ValueError

 

class Computer(Player):

  def getChoice(self):

      return randrange(0,3)

 

 

>
> def compare_objects(human, computer):
>   print "Human picked ", human.choice
>   print "Computer picked", computer.choice
>   results = { 'rock' : {'rock' : 'draw', 'paper': 0,
>                  'scissors': 1},
>                  'paper' : {'rock' : 1, 'paper': 'draw', 'scissors':
>                   0},
>                  'scissors' : {'rock' : 0, 'paper' : 1, 'scissors' :
>                  'draw'}
>              }
>
>   outcome = results[human.choice][computer.choice]
>   if outcome == 0:
>     print "Computer Wins!"
>     computer.points = computer.points + 1
>   elif outcome == 1:
>     print "Human Wins!"
>     human.points = human.points + 1
>   else:
>     print "Draw!"

 

By using the number format of storage and the

dictionary in the class you can simplify that

as in show below using lists.

> I actually figured out how to build the 2x2 matrix.
> I'm quite proud of this. 

 

A nested dictionary is one way. Another is to use numbers

to represent the choices and outcomes and create a nested

list structure nested list

 

rps = {0:'Rock',1:'Paper',2:'Scissors'}

draw,loss,win = 0,1,2

outcomes = [ [0,1,2], [2,0,1], [1,2,0] ]

 

computer = randrange(0,3)

human = randrange(0,3)

result = outcomes[computer][human]

if result == draw: print 'Draw'

elif result == loss: print 'Computer lost with', rps[computer]

elif result == win: print 'Computer won with', rps[computer]

 

The dictionary is more verbose but does have more readable

code.

 

I hope somebody finds at least some of that interesting! :-)

I guess what I'm really trying to show is how

choosing different data structures makes a big

difference to how the code looks.

 

Alan G.

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