Iterate over unknown object attributes in Python

Question

I have a class as such below. However, the attribute names remain unknown. How, under this circumstance, do a make a class iterator? Basic examples point to __iter__ and next() having some knowledge of the class's attributes as does the example in the pydocs.

class Foo(object):
    def __init__(self, dictionary):
        for k, v in dictionary.iteritems():
            setattr(self, k, v)

I would like to iterate through each object attribute something like so:

bar = Foo(dict)
for i in bar:
    bar[i]

Abhijit · Accepted Answer · 2014-07-21 17:53:00Z

3

As @TheSoundDefense suggested you can use the vars() built-in to list all the attributes of the object. The following answer extends the idea with an example of using it in your case

Implementation

class Foo(object):
    def __init__(self, dictionary):
        for k, v in dictionary.iteritems():
            setattr(self, k, v)
    def __iter__(self):
        return iter(vars(self))

Demo

foo = Foo({'X':1, 'Y':2, 'Z':3})
for elem in foo:
    print elem

Output

Y
X
Z

answered Jul 21, 2014 at 17:53

Abhijit

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1 Comment

TheSoundDefense Over a year ago

And I am defeated by an overlong lunch. Good answer.

TheSoundDefense · Accepted Answer · 2014-07-21 17:38:06Z

3

You may want the vars() function here. That will return a dictionary of attribute names and values for any arbitrary object. Just use vars(obj_name).

answered Jul 21, 2014 at 17:38

TheSoundDefense

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2 Comments

wearp Over a year ago

Are you suggesting to use vars() with the class as part of making the it iterable?

TheSoundDefense Over a year ago

Yes, to generate the initial dictionary. Then you could iterate over them how you like, probably with iteritems. Mainly I was addressing how to obtain the attributes if the names are unknown. I'll post an update when I get back from lunch, unless a better answer comes along.

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