Variable passing using super() in Python

Question

I thought I understood how this would work but apparently I don't. Take this example:

File 1 (sandbox.py):

from module1 import Testy

class Sandy(Testy):
    def run(self):
        print("This is value of x in Sandy: %d" % x)
        super(Sandy, self).mymet()

if __name__ == "__main__":
    x = 4
    test = Sandy()
    test.run()

File 2 (module1.py):

class Testy(object):
    def mymet(self):
        print("This is the value of x in Testy %d: " % x)

This is what I receive back in the console when running sandbox.py:

This is value of x in Sandy: 4
NameError: global name 'x' is not defined

Is the best/only way of doing this to pass the x argument explicitly to mymet() in the parent class?

That's not how scoping works. You can't access locals from other functions. — internet_user
– internet_user, Commented Mar 22, 2018 at 17:56

001 · Accepted Answer · 2018-03-22 17:57:39Z

2

You need to pass it to both functions as a parameter:

class Testy(object):
    def mymet(self, x):
        print("This is the value of x in Testy %d: " % x)

class Sandy(Testy):
    def run(self, x):
        print("This is value of x in Sandy: %d" % x)
        super(Sandy, self).mymet(x)

if __name__ == "__main__":
    x = 4
    test = Sandy()
    test.run(x)

answered Mar 22, 2018 at 17:57

001

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2 Comments

JPow Over a year ago

Thanks for the help, this is obviously a fundamental misunderstanding on my part. I believe in my case above I would only need to pass x into mymet() and wouldn't need to pass x into Sandy().run(). I guess I assumed this could be made available without explicitly passing it through - but seems I'm wrong.

001 Over a year ago

@JPow You could bypass test.run(x) and call mymet directly with test.mymet(x) but you still need to pass it as a parameter.

Mike Tung · Accepted Answer · 2018-03-22 17:57:15Z

-1

The issue is your base class Testy

the variable x is not defined in class scope and so it doesn't exist in your subclasses.

class Testy(object):
    self.x = 4
    def mymet(self):
        print("This is the value of x in Testy %d: " % self.x)

answered Mar 22, 2018 at 17:57

Mike Tung

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