What's the best way to get referenced object (variable level)

Question

Let's assume, the following case:

class foo(object):
    def __init__(self, ref=None):
        self.ref = ref

    def __str__(self):
        return "I'm foolish"

f = foo()
f.ref = foo()
f.ref.ref = foo()
f.ref.ref.ref = foo()

Trying print(getattr(f, "ref.ref.ref"))

raises 'foo' object has no attribute 'ref.ref.ref'.

So, I resolved the issue with the following function:

def get_ref(ref_attr):
    for attr in ref_attr.split('.'):
        print(getattr(f, attr))

get_ref("ref.ref.ref") retruns the expected result:
I'm foolish
I'm foolish
I'm foolish

I wonder myself, if is an another way to do this or a built-in method that i could used.

Thanks.

score 1 · Accepted Answer · answered Jun 14 '13 at 09:25

1

That's not doing what you think: it's getting the first element each time. It only appears to work because all the levels are called "ref". If you called them 'foo.bar.baz' it would fail. You need to actually use the element from the last iteration each time:

def get_ref(ref_attr):
    item = f
    for attr in ref_attr.split('.'):
        item = getattr(item, attr)
        print item

But no, there's no built-in way of doing this.

answered Jun 14 '13 at 09:25

Daniel Roseman

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2

`reduce(getattr, attribute_names, object)` – Bakuriu Jun 14 '13 at 09:55
That's excellent, @Bakuriu. For some reason I never think of using `reduce`. – Daniel Roseman Jun 14 '13 at 10:01

What's the best way to get referenced object (variable level)

1 Answers1