Calling instance method recursively in python

Question

I'm trying to call the instance method of objects inside a dictionary who have the objects themselves, all are from the same class. But i have a infinite recursion, i think that 'self' doesn't change and reference the first object all the time.

class Foo():
    name = 'name'
    foo_objects = {}
    def print_name(self):
        output = self.name
        for key, value in self.foo_objects.items():
            output += value.print_name()
        return output

I'm using it like this:

def main():
    foo = Foo()
    foo.foo_objects['key'] = Foo()
    print foo.print_name()

if __name__ == '__main__':
    sys.exit(main())

And i get this error:

  ...etc...
    output += value.print_name()
  File "C:\dev\python\projects\test\test.py", line 41, in print_name
    output += value.print_name()
  File "C:\dev\python\projects\test\test.py", line 41, in print_name
    output += value.print_name()
RuntimeError: maximum recursion depth exceeded

What´s wrong? What I'm not understanding of python recursion? How can be do? Thanks for any help, and excuse me my bad english.

jim-minter · Accepted Answer · 2013-03-31 11:51:21Z

4

You've defined name and foo_objects as class variables, not instance variables -- i.e. they are currently shared between all instances of the Foo class.

Change:

class Foo():
  name = 'name'
  foo_objects = {}
...

to:

class Foo():
  def __init__(self):
    self.name = 'name'
    self.foo_objects = {}
...

and they will become instance variables as I suspect you wanted them to be.

answered Mar 31, 2013 at 11:51

jim-minter

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1 Comment

ecdani Over a year ago

Thanks!!, Now i know about class attributes and instance attributes in python.

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