Iterate over an object's "public" attributes

Question

Recently, I find myself writing code like this:

for name in dir( object ):
    if name.startswith( '__' ) : continue
    ...

Is there a more pythonic way to access the object's "public" namespace?

Answer 1

You could use the vars function instead.

For example:

>>> class C(object):
...   def __init__(self):
...     self.__foo = 'foo'
... 
>>> c = C()
>>> dir(c)
['_C__foo', '__class__', '__delattr__', '__dict__', '__doc__', '__format__', 
'__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__',    
'__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__',    
'__weakref__']
>>> vars(c)
{'_C__foo': 'foo'}

Note that, as Niklas R has pointed out, variables with a single underscore are also considered private. However the vars() function has the advantage of eliminating all but the instance variables.

Answer 2

You can prepare list of "public" attributes (as list or as generator) before:

>>> public_props = (name for name in dir(object) if not name.startswith('_'))
>>> for name in public_props:
    print name

But please read a note about dir() function in the documentation:

Note Because dir() is supplied primarily as a convenience for use at an interactive prompt, it tries to supply an interesting set of names more than it tries to supply a rigorously or consistently defined set of names, and its detailed behavior may change across releases. For example, metaclass attributes are not in the result list when the argument is a class.

You should also be aware, that any class can implement __dir__() method that may return a list of names that do not necessarily correspond to the names of the attributes. In other words, dir(something) does not guarantee that the result will return attributes of something.

Answer 3

Rather than an exclusion branch using the continue keyword, iterating over a comprehension of public names directly seems more Pythonic. But it could just be a matter of taste, it's admittedly not much better than what you already have.

public_names = (n for n in dir(object) if not n.startswith('_'))
for attr in public_names:
    ...

Note: Single underscore attributes are also not "public".