R equivalent to the Python function "dir"?

Question

Is there a function in R that can tell me the attributes of a given object (or class)?

Consider the "dir" function in python when passed the file class:

>>> dir(file)
['__class__', '__delattr__', '__doc__', '__enter__', '__exit__', 
 '__format__', '__getattribute__', '__hash__', '__init__', '__iter__',
 '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__',
 '__sizeof__', '__str__', '__subclasshook__', 'close', 'closed',
 'encoding', 'errors', 'fileno', 'flush', 'isatty', 'mode', 'name',
 'newlines', 'next', 'read', 'readinto', 'readline', 'readlines',
 'seek', 'soft space', 'tell', 'truncate', 'write', 'writelines',
 'xreadlines']

Maybe there is an equivalent of type as well(?)

>>> type(1)
<type 'int'>

Answer 1

R makes several different object oriented systems available to you, so if you don't know what species of object you're dealing with, you'll first need to determine whether it is one of S3, S4, or RC. Use isS4(x) and is(x, 'refClass') for this. If it's not S4 and not RC, it's S3. See Hadley's Advanced R chapter on object oriented programming for more information.

For S3 and S4 objects there are several functions you need to call to get information equivalent to Python's dir. All of these methods will require you to supply the name of the class of the object as an argument, which you can determine with the class function.

For methods, use methods(class=class(x)) for S3 objects and showMethods(class=class(x)) for S4 objects. To reveal "attribute" names/values, use attributes(x) for S3 objects and getSlots(class(x)) for S4 objects. Note, getSlots will only show the slot names and types, not their values. To access the values, you'll have to use slot, but these values should also print when you simply print the object to the console.