CODEWITHSUNDEEP
pythonclassoop
neversaint
neversaint

Reputation: 64064

How can I make a method takes the value(s) from another method from within the same class in Python

I have the following Class and the corresponding method.

#!/usr/bin/env python
class Foo:
    def __init__(self, x):
        self.x = x
    def bar(self):
        bar_out = self.x + 5
        return bar_out
    def qux(self):
        qux_out = bar_out + 3
        return qux_out

def main():
    """docstring for main"""
    f = Foo(5)

    main_bar_out = f.bar()
    print main_bar_out

    #main_qux_out = f.qux()
    #print main_qux_out



if __name__ == '__main__':
    main()

What I want to do here is to make the method a=qux takes the value from bar, process it and return a value. So that the final output of main_qux_out is 13. How can I do this correctly?

Note that here I want qux() to take the value automatically from bar(), without passing any parameter.

Update

Thanks for @thefourtheye, for the response. I have further questions.

Let say if I want to have bar() to return two or more values (this can be string, string, list or dict), how can I call it from qux(). I tried this but failed. 

#!/usr/bin/env python
class Foo:
    def __init__(self, x):
        self.x = x
    def bar(self):
        self.bar1_out = self.x + 5
        self.bar2_out = self.x + 1
        return (self.bar1_out,self.bar2_out)
    def qux(self):
        self.qux_out1 = self.bar1_out() + 3
        self.qux_out2 = self.bar2_out() + 6
        return ( self.qux_out1, self.qux_out2)

def main():
    """docstring for main"""
    f = Foo(5)

    mbr_out1, mbr_out2 = f.bar()
    print mbr_out1, "\t", mbr_out2

    mqx_out1, mqx_out2 = f.qux()
    print mqx_out1, "\t", mqx_out2


if __name__ == '__main__':
    main()

This should print:

10  6
13  12

Upvotes: 1

Views: 61

Answers (2)

thefourtheye
thefourtheye

Reputation: 239653

You cannot access a local variable defined in one function, from another function. But you can invoke the bar function and use the return value like this

def qux(self):
    return self.bar() + 3

If you want to decide which value to use (bar or the value passed as parameter) dynamically, then you can do something like this

def qux(self, myvalue = None):
    if myvalue is not None:
        return myvalue + 3
    else:
        return self.bar() + 3

If you don't pass any value to qux, myvalue will be default take None as its value. Inside the function, we check if it is not None, then we use the value as it it, otherwise we call self.bar() and use that value.

If you are planning to return two values from bar, then you can unpack them like this

def qux(self, myvalue = None):
    first, second = myvalue or self.bar()
    return first + 3, second + 6

Here myvalue or self.bar() makes sure that we take self.bar() if myvalue is None.

Note: If you are planning to do this way, then you need pass two values for myvalue as well, like this

self.qux((1, 2))

Upvotes: 3

user2913685
user2913685

Reputation: 71

methods inside of a class can only access variables of that class or variables defined inside the method. What you ought to do is either make bar a variable of the class (instead of being part of the method)

def bar(self):
    self.bar_out = self.x + 5
    return self.bar_out

or call bar() and use the output in the calculation

def qux(self):    
    qux_out = self.bar() + 3

Upvotes: 1

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