Passing variables between methods in Python?

Question

I have a class and two methods. One method gets input from the user and stores it in two variables, x and y. I want another method that accepts an input so adds that input to x and y. When I run calculate(z) for some number z, it gives me errors saying the global variables x and y aren't defined. Obviously this means that the calculate method isn't getting access to x and y from getinput(). What am I doing wrong?

class simpleclass (object):
    def getinput (self):
            x = input("input value for x: ")
            y = input("input value for y: ")
    def calculate (self, z):
            print x+y+z

Does this answer your question? [How to share variables between methods in a class?](https://stackoverflow.com/questions/7670415/how-to-share-variables-between-methods-in-a-class) — outis, Dec 19 '21 at 19:39

score 16 · Answer 1 · answered Mar 01 '12 at 16:33

16

These need to be instance variables:

class simpleclass(object):
   def __init__(self):
      self.x = None
      self.y = None

   def getinput (self):
        self.x = input("input value for x: ")
        self.y = input("input value for y: ")

   def calculate (self, z):
        print self.x+self.y+z

answered Mar 01 '12 at 16:33

turtlebender

1,887
14
16

2

+1 for most correct answer illustrating use of the __init__() method. – Li-aung Yip Mar 01 '12 at 16:38

score 5 · Answer 2 · answered Mar 01 '12 at 16:32

5

You want to use self.x and self.y. Like so:

class simpleclass (object):
    def getinput (self):
            self.x = input("input value for x: ")
            self.y = input("input value for y: ")
    def calculate (self, z):
            print self.x+self.y+z

answered Mar 01 '12 at 16:32

Li-aung Yip

11,952
5
31
49

@DSM: D'oh! Good catch. Edited to fix. – Li-aung Yip Mar 01 '12 at 16:37

Karoly Horvath · Answer 3 · 2012-03-01T16:39:37.697

3

x and y are local variables. they get destroyed when you move out from the scope of that function.

class simpleclass (object):
    def getinput (self):
            self.x = raw_input("input value for x: ")
            self.y = raw_input("input value for y: ")
    def calculate (self, z):
            print int(self.x)+int(self.y)+z

edited Mar 01 '12 at 16:39

answered Mar 01 '12 at 16:34

Karoly Horvath

91,854
11
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173

Probably want to get a number from the string at some point if you're switching to raw_input. – DSM Mar 01 '12 at 16:36

score 2 · Answer 4 · answered Mar 01 '12 at 16:33

2

Inside classes, there's a variable called self you can use:

class Example(object):
    def getinput(self):
        self.x = input("input value for x: ")
    def calculate(self, z):
        print self.x + z

answered Mar 01 '12 at 16:33

Brendan Long

51,248
19
139
179

score 0 · Answer 5 · answered Jun 28 '17 at 14:07

class myClass(object):

    def __init__(self):

    def helper(self, jsonInputFile):
        values = jsonInputFile['values']
        ip = values['ip']
        username = values['user']
        password = values['password']
        return values, ip, username, password

    def checkHostname(self, jsonInputFile):
       values, ip, username, password = self.helper
       print values
       print '---------'
       print ip
       print username
       print password

the init method initializes the class. the helper function just holds some variables/data/attributes and releases them to other methods when you call it. Here jsonInputFile is some json. the checkHostname is a method written to log into some device/server and check the hostname but it needs ip, username and password for that and that is provided by calling the helper method.

Passing variables between methods in Python?

5 Answers5

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