global methods or functions in python

Question

I am making a small game in Python using pythonista on my ipad. I made a vector class that contains the coordinates and several functions to add, get a length, set a length. I have another class called Game in which I have my game variables and functions. I can define a vector lets say

self.pos=vector(200,200)

But if I want to work out the length, I can't call the getlength function because I'm not in the right class.

Example (I've taken out most of the code):

class vector(objet):
    def __init(self,x,y):
        self.x=x
        self.y=y

   def getlength(self):
       return sqrt(self.x**2+self.y**2)

  def addvec(self,a,b):
   return vector(a.x+b.x,a.y,b.y)


class Game(object):
    def __init__(self):
        self.pos=vector(200,200)
        self.pos=vector(200,200)

    def loop(self):
        ## here i want something like d= length of self.pos !!

class MyScene(Scene):
    def setup(self):
        self.game=Game()

    def draw(self):
        self.game.loop()  

run(MyScene())

Thanks, Nicolas

EDIT : the call

sum=addvec(self.pos,self.pos2)

obviously doesn't work because self is a Game class. How can I do it?

self.pos.getlength? You neither want nor need it to be a global function - it's a useful instance method. — jonrsharpe
– jonrsharpe, Commented May 23, 2014 at 17:24
Please use 4 spaces to set an indentation level. UPD: That's better. — vaultah
– vaultah, Commented May 23, 2014 at 17:24

BenMorel · Accepted Answer · 2014-07-01 19:31:01Z

4

Why do you use two arguments for the getLength function? The second one is a vector (I assume) so it would be better to use:

def getLength(self):
    return sqrt(self.x**2+self.y**2)

and then just call:

d = self.pos.getLength()

If you would want to add two vectors together you would do something like this:

def add(self,other_vector):
    return vector(self.x+other_vector.x,self.y+other_vector.y)

so you would call:

sum = self.pos.add(some_other_vector)

BTW: Classes should always be written in CamelCase. And maybe you should read something about object oriented programming in python: http://code.tutsplus.com/articles/python-from-scratch-object-oriented-programming--net-21476

edited Jul 1, 2014 at 19:31

BenMorel

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answered May 23, 2014 at 17:28

wastl

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1 Comment

nwins Over a year ago

Thanks, that works ! Sorry if I and not very good at this...if I want to add two vectors with a function in the vector class. 'code' def addvec(self,a,b): return vector(a.x+b.x,a.y,b.y) the call sum=addvec(self.pos,self.pos2) obviously doesn't work because self is a Game class. How can I do it?

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