Why does `getattr` not support consecutive attribute retrievals?

Question

class A(): pass

a = A()
b = A()

a.b = b
b.c = 1

a.b     # this is b
getattr(a, \"b\") # so is this

a.b.c   # this is 1   
getattr(a, \"b.c\") # this raises an Attrib         


        

Answer 1

Python's built-in reduce function enables the functionality you're looking for. Here's a simple little helper function that will get the job done:

class NoDefaultProvided(object):
    pass

def getattrd(obj, name, default=NoDefaultProvided):
    """
    Same as getattr(), but allows dot notation lookup
    Discussed in:
    http://stackoverflow.com/questions/11975781
    """

    try:
        return reduce(getattr, name.split("."), obj)
    except AttributeError, e:
        if default != NoDefaultProvided:
            return default
        raise

Test proof;

>>> getattrd(int, 'a')
AttributeError: type object 'int' has no attribute 'a'

>>> getattr(int, 'a')
AttributeError: type object 'int' has no attribute 'a'

>>> getattrd(int, 'a', None)
None

>>> getattr(int, 'a', None)
None

>>> getattrd(int, 'a', None)
None

>>> getattrd(int, '__class__.__name__')
type

>>> getattrd(int, '__class__')