Python 3 Functions - List Values for Other Functions

Question

I am working on a very simple text based adventure game. I have been able to do the basics where the player can move from room to room. To enhance the game I wanted a simple combat system but I am having trouble implementing a system which will keep the players health score. I have provided a sample of how the code is at the moment and added comments.

def update_score(x): #after the player has a combat round the variable 'a'is updated with remianing hit points
    a = []
    a.append(x)

def hit_points(): #when the player is in combat and takes a hit, 2 points are deducted and it is passed to the updated score function
    y -= 2
    updated_score(y)

def Continue():
    #how can i then reference the updated score in another function. If the player goes into another battle, the remaining battle points will have to be used and deducted from

I have only just started getting to grips with functions and would like to know if it is possible to pass the updated values from the updated_score function to other functions or when the hit point function is called again.

I am trying to avoid using Global variables.

Any help much appreciatted

The normal way would be to return the values you need outside the function and to pass the values you need to use in other functions as arguments to those functions. — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Jul 2, 2018 at 16:52
I am just about to start using classes an objects. I was thinking it would be an easier method. — Zeeman
– Zeeman, Commented Jul 2, 2018 at 16:53

bphi · Accepted Answer · 2018-07-02 16:53:02Z

3

Try using a class

class Player:
    def __init__(self):
        self.hit_points = 100

    def take_hit(self):
        self.hit_points -= 2

p = Player()

print(p.hit_points)
>>> 100

p.take_hit()

print(p.hit_points)
>>> 98

answered Jul 2, 2018 at 16:53

bphi

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Comments

i.terrible · Accepted Answer · 2018-07-02 16:54:40Z

0

Write a class. Consider:

class GameState:
   score = 0
   life = 10

   def update_score(self, x):
      self.score += x  # you can use negative values here too and perform various checks etc.  

   def hit_points(self):
      self.life -= 2

Your data is stored in the class and you can manipulate it with the methods. No issues with polluting global scope.

answered Jul 2, 2018 at 16:54

i.terrible

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2 Comments

user5051310 Over a year ago

Gamestate seems like to broad a place to put life points. Shouldn't it be more specific(like the other answer)?

i.terrible Over a year ago

you're right, I was assuming it's a simple game and naming was not the point.

kosnik · Accepted Answer · 2018-07-02 16:56:47Z

0

I assume that your variable y is the one you need to update and access again in the future. But since y is of type int cannot be passed by reference to functions, which means that you cannot access it's updated value unless you define it as a global. Here is a good intro to global variables

https://www.geeksforgeeks.org/global-local-variables-python/

And here is a very detailed post about which variables are passed by value and which by reference in python

https://jeffknupp.com/blog/2012/11/13/is-python-callbyvalue-or-callbyreference-neither/

In your case you should just make the following change in the definition of hit_points

def hit_points():
    global y
    y -= 2
    updated_score(y)

However, for a big project I wouldn't suggest to use global. This is a typical case where you should define a class and make y a member variable

class Game:
    def __init__(self):
        self._y = 0

    def hit_point(self):
        self._y -= 2

answered Jul 2, 2018 at 16:56

kosnik

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1 Comment

juanpa.arrivillaga Over a year ago

That link is very clear that variables are neither passed by value nor passed by reference, and are always passed the same way.

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