Traversing objects in python

Question

How can I write this code without repeating myself indefinitely?

fields = row.split('__')

if len(fields) == 1:
    foo = getattr(bundle.obj, fields[0])
elif len(fields) == 2:
    foo = getattr(getattr(bundle.obj, fields[0]), fields[1])
elif len(fields) == 3:
    foo = getattr(getattr(getattr(bundle.obj,
                            fields[0]), fields[1]), fields[2])
# etc ..

Answer 1

Use reduce():

foo = reduce(getattr, fields, bundle.obj)

or a simple loop:

foo = bundle.obj
for field in fields:
    foo = getattr(foo, field)