Programming
python class attributes
Updated Sun, 24 Jul 2022 21:39:43 GMT

Printing all the attributes in a class


Please do not ask how I get myself into this situation. Lets say I have a class called ccollection.

this class has the following attributes at runtime:

ccollection.a.b.x = 1
ccollection.a.b.y = 3
ccollection.a.b.z = 4
...
ccollection.a.c = 3
ccollection.b = 3

this class will be setup dynamically as described above. so there is no way to know the attributes in the class before hand.

Now I would like to print all the attributes in this class, for example:

ccollection.a.b should print

ccollection.a.b.x = 1
ccollection.a.b.y = 3
ccollection.a.b.z = 4

and ccollection.a should print

ccollection.a.b.x = 1
ccollection.a.b.y = 3
ccollection.a.b.z = 4
ccollection.a.c = 3

I think you get the idea. Each print should starts printing all the elements at the same level and below. I am looking for a way to recursively traverse all the attributes (which is a tree-like data structure)

Solution

This situation really calls for refactoring. You are using an object that is not designed as a container. Instead, use a container such as a dict or a class that inherits from dict.

If you must use the current setup, I agree with Blckknght that the most promising approach appears to use dir.

class CCollection(object):
  def get_children_strings(self):
    list_of_strings = []
    for attr_name in dir(self):
      if attr_name not in dir(CCollection()):
        attr = getattr(self, attr_name)
        if hasattr(attr, 'get_children_strings'):
          list_of_strings.extend(["." + attr_name + child_string for child_string in attr.get_children_strings()])
        else:
          list_of_strings.append("." + attr_name + " = " + str(attr))
    return list_of_strings
  def print_tree(self, prefix):
    print [prefix + s for s in self.get_children_strings()]

Then you can 

m = CCollection()
m.a = CCollection()
m.a.b = CCollection()
m.a.b.x = 1
m.a.b.y = 2
m.a.c = 3
m.d = 4
m.print_tree("m")
m.a.print_tree("m.a")
m.a.b.print_tree("m.a.b")

and get the outputs:

>>> m.print_tree("m")
['m.a.b.x = 1', 'm.a.b.y = 2', 'm.a.c = 3', 'm.d = 4']
>>> m.a.print_tree("m.a")
['m.a.b.x = 1', 'm.a.b.y = 2', 'm.a.c = 3']
>>> m.a.b.print_tree("m.a.b")
['m.a.b.x = 1', 'm.a.b.y = 2']

To take this further, you probably would want to use a class with tree-traversal functions. You could automatically generate the info currently being passed in via the prefix argument to the print_tree function, if you had a function to get the parent node, a guarantee of no loops, and a class variable holding the node's name.

Comments (1)

  • +0 – one of my old questions but a great answer none the less. — Jul 10, 2013 at 21:02  

External Links

External links referenced by this document:

References