Getting attributes of a class

Question

I want to get the attributes of a class  say   class MyClass      a    12    b    34     def myfunc self       return self a   using MyClass   dict   gives me a list of attributes and functions  and even functions like   module   and   doc    While MyClass     dict   gives me an empty dict unless I explicitly set an attribute value of that instance   I just want the attributes  in the example above those would be  a and b

User · Answer

Python 2  amp  3  whitout imports  filtering objects by their address  Solutions in short   Return dict  attribute name  attribute value   objects filtered  i e   a   1   b    2  2    c    3  3     k  val for k  val in self   dict   items   if not str hex id val    in str val     Return list  attribute names   objects filtered  i e   a    b    c    d     k for k  val in self   dict   items   if not str hex id val    in str val     Return list  attribute values   objects filtered  i e  1   2  2    3  3    4  4     val for k  val in self   dict   items   if not str hex id val    in str val       Not filtering objects  Removing the if condition  Return   a   1   c    3  3    b    2  2    e    lt function  lt lambda gt  at 0x7fc8a870fd70 gt    d    4  4    f    lt object object at 0x7fc8abe130e0 gt      k  val for k  val in self   dict   items        Solution in long  As long as the default implementation of   repr   is not overridden the if statement will return True if the hexadecimal representation of the location in memory of val is in the   repr   return string   Regarding the default implementation of   repr   you could find useful this answer  In short   def   repr   self       return   lt  0   1  object at  2  gt   format        self   module    type self    name    hex id self      Wich returns a string like    lt   main   Bar object at 0x7f3373be5998 gt    The location in memory of each element is got via the id   method    Python Docs says about id        Return the    identity    of an object  This is an integer which is guaranteed to be unique and constant for this object during its lifetime  Two objects with non-overlapping lifetimes may have the same id   value       CPython implementation detail  This is the address of the object in   memory      Try by yourself  class Bar       def   init   self            self a   1         self b    2  2          self c    3  3          self d    4  4          self e   lambda   5          self f   object           str   or   repr   as you prefer     def   str   self           return      format                 Solution in Short Number 1              k  val for k  val in self   dict   items   if not str hex id val    in str val                 Main print Bar      Output     a   1   c    3  3    b    2  2    d    4  4       Note     Tested with Python 2 7 13 and Python 3 5 3 In Python 2 x  iteritems   is preferred over  items

User · Answer

This can be done without inspect  I guess   Take the following class    class Test     a   1    b   2     def   init   self        self c   42      staticmethod    def toto         return  toto      def test self        return  test    Looking at the members along with their types   t   Test   l      x  eval  type x  s    name      x   for x in dir a          gives        doc      NoneType         init      instancemethod         module      str       a    int       b    int       c    int       test    instancemethod       toto    function      So to output only the variables  you just have to filter the results by type  and names not starting with       E g   filter lambda x  x 1  not in   instancemethod    function   and not x 0  startswith        l      a    int      b    int      c    int      actual result   That s it   Note  if you re using Python 3  convert the iterators to lists   If you want a more robust way to do it  use inspect

User · Answer

import re  class MyClass      a    12      b    34       def myfunc self           return self a  attributes    a for a  v in MyClass   dict   items                 if not re match   lt function    gt    str v                 and not  a startswith       and a endswith           For an instance of MyClass  such as  mc   MyClass     use type mc  in place of MyClass in the list comprehension   However  if one dynamically adds an attribute to mc  such as mc c    42   the attribute won t show up when using type mc  in this strategy   It only gives the attributes of the original class   To get the complete dictionary for a class instance  you would need to COMBINE the dictionaries of type mc    dict   and mc   dict     mc   MyClass   mc c    42     Python 3 5 combined dict      type mc    dict      mc   dict       Or Python  lt  3 5 def dict union d1  d2       z   d1 copy       z update d2      return z  combined dict   dict union type mc    dict    mc   dict     attributes    a for a  v in combined dict items                 if not re match   lt function    gt    str v                 and not  a startswith       and a endswith

User · Answer

Getting only the instance attributes is easy  But getting also the class attributes without the functions is a bit more tricky  Instance attributes only If you only have to list instance attributes just use for attribute  value in my instance   dict   items     gt  gt  gt  from   future   import  absolute import  division  print function   gt  gt  gt  class MyClass object         def   init   self           self a   2         self b   3       def print instance attributes self           for attribute  value in self   dict   items              print attribute       value       gt  gt  gt  my instance   MyClass    gt  gt  gt  my instance print instance attributes   a   2 b   3  gt  gt  gt  for attribute  value in my instance   dict   items          print attribute       value      a   2 b   3  Instance and class attributes To get also the class attributes without the functions  the trick is to use callable    But static methods are not always callable  Therefore  instead of using callable value  use callable getattr MyClass  attribute   Example from   future   import  absolute import  division  print function   class MyClass object      a    quot 12 quot     b    quot 34 quot                  class attributes     def   init   self  c  d        self c   c      self d   d             instance attributes      staticmethod    def mystatic             static method        return MyClass b     def myfunc self          non-static method      return self a     def print instance attributes self        print   instance attributes         for attribute  value in self   dict   items            print attribute       value      def print class attributes self        print   class attributes         for attribute in self   dict   keys           if attribute  2                    value   getattr self  attribute           if not callable value              print attribute       value   v   MyClass 4 2  v print class attributes   v print instance attributes    Note  print class attributes   should be  staticmethod        but not in this stupid and simple example  Result for python2   python2   print attributes py  class attributes  a   12 b   34  instance attributes  c   4 d   2  Same result for python3   python3   print attributes py  class attributes  b   34 a   12  instance attributes  c   4 d   2

User · Answer

I don t know if something similar has been made by now or not  but I made a nice attribute search function using vars    vars   creates a dictionary of the attributes of a class you pass through it   class Player        def   init   self           self name    Bob          self age   36         self gender    Male   s   vars Player     From this point if you want to print all the attributes  just do print s    If the class has a lot of attributes and you want to be able to pick 1 to see  run this function def play        ask   input  What Attribute  gt          for key  value in s items            if key    ask              print  self          format key  value               break     else          print  Couldn t find an attribute for self     format ask     I m developing a pretty massive Text Adventure in Python  my Player class so far has over 100 attributes  I use this to search for specific attributes I need to see

User · Answer

myfunc is an attribute of MyClass  That s how it s found when you run   myinstance   MyClass   myinstance myfunc     It looks for an attribute on myinstance named myfunc  doesn t find one  sees that myinstance is an instance of MyClass and looks it up there   So the complete list of attributes for MyClass is    gt  gt  gt  dir MyClass      doc        module      a    b    myfunc      Note that I m using dir just as a quick and easy way to list the members of the class  it should only be used in an exploratory fashion   not in production code   If you only want particular attributes  you ll need to filter this list using some criteria  because   doc      module    and myfunc aren t special in any way  they re attributes in exactly the same way that a and b are   I ve never used the inspect module referred to by Matt and Borealid  but from a brief link it looks like it has tests to help you do this  but you ll need to write your own predicate function  since it seems what you want is roughly the attributes that don t pass the isroutine test and don t start and end with two underscores   Also note  by using class MyClass    in Python 2 7 you re using the wildly out of date old-style classes  Unless you re doing so deliberately for compatibility with extremely old libraries  you should be instead defining your class as class MyClass object    In Python 3 there are no  old-style  classes  and this behaviour is the default  However  using newstyle classes will get you a lot more automatically defined attributes    gt  gt  gt  class MyClass object           a    12          b    34          def myfunc self               return self a  gt  gt  gt  dir MyClass      class        delattr        dict        doc        format        getattribute        hash        init        module        new        reduce        reduce ex        repr        setattr        sizeof        str        subclasshook        weakref      a    b    myfunc

User · Answer

You can use MyClass   attrs     It just gives all the attributes of that class  Nothing more

User · Answer

You can use dir   in a list comprehension to get the attribute names   names    p for p in dir myobj  if not p startswith         Use getattr   to get the attributes themselves   attrs    getattr myobj  p  for p in dir myobj  if not p startswith

User · Answer

MyClass     class     dict    However  the  right  was to do this is via the inspect module

User · Answer

If you want to  get  an attribute  there is a very simple answer  which should be obvious  getattr  class MyClass object   a    12  b    34  def myfunc self       return self a   gt  gt  gt  getattr MyClass   a    12    gt  gt  gt  getattr MyClass   myfunc    lt function MyClass myfunc at 0x10de45378 gt    It works dandy both in Python 2 7 and Python 3 x   If you want a list of these items  you will still need to use inspect

User · Answer

I recently needed to figure out something similar to this question  so I wanted to post some background info that might be helpful to others facing the same in future   Here s how it works in Python  from https   docs python org 3 5 reference datamodel html the-standard-type-hierarchy    MyClass is a class object  MyClass   is an instance of the class object  An instance s   dict   only hold attributes and methods specific to that instance  e g  self somethings   If an attribute or method is part of a class  it is in the class s   dict    When you do MyClass     dict    an instance of MyClass is created with no attributes or methods besides the class attributes  thus the empty   dict    So if you say print MyClass   b   Python first checks the new instance s dict MyClass     dict    b   and fails to find b  It then checks the class MyClass   dict    b   and finds b   That s why you need the inspect module  to emulate that same search process

User · Answer

I know this was three years ago  but for those who are to come by this question in the future  for me   class name attribute    works just fine

User · Answer

Why do you need to list the attributes  Seems that semantically your class is a collection  In this cases I recommend to use enum   import enum  class myClass enum Enum        a    12       b    34    List your attributes  Nothing easier than this   for attr in myClass      print  Name   Value    attr name  attr value

User · Answer

My solution to get all attributes  not methods  of a class  if the class has a properly written docstring that has the attributes clearly spelled out    def get class attrs cls       return re findall r  w             cls   dict      doc        This piece cls   dict      doc     extracts the docstring of the class

User · Answer

def props cls        return  i for i in cls   dict   keys   if i  1           properties   props MyClass

User · Answer

The following is what I want  Test Data class Base      b    b    class MyClass Base       a    12       def   init   self  name           self name   name       classmethod     def c cls                     property     def p self           return self a      def my fun self           return self name  print  name for name  val in inspect getmembers MyClass  if not name startswith      and not callable val       need  import inspect  print    for   in dir MyClass  if not   startswith      and not callable getattr MyClass          both are equ    a    b    p    my instance   MyClass  c   print    for   in dir my instance  if not   startswith      and not callable getattr my instance            a    b    name    p

User · Answer

Another simple solution  class Color const       BLUE   0     RED   1     GREEN   2       classmethod     def get all cls           return  cls BLUE  cls RED  cls GREEN    Usage  Color get all

User · Answer

Try the inspect module  getmembers and the various tests should be helpful   EDIT   For example   class MyClass object       a    12      b    34      def myfunc self           return self a   gt  gt  gt  import inspect  gt  gt  gt  inspect getmembers MyClass  lambda a not inspect isroutine a         class     type        dict        lt dictproxy     dict      lt attribute    dict    of  MyClass  objects gt         doc     None        module        main           weakref      lt attribute    weakref    of  MyClass  objects gt       a    34       b    12       myfunc    lt function   main   myfunc gt   gt         doc     None        module        main           weakref      lt attribute    weakref    of  MyClass  objects gt       a    34       b    12      Now  the special methods and attributes get on my nerves- those can be dealt with in a number of ways  the easiest of which is just to filter based on name    gt  gt  gt  attributes   inspect getmembers MyClass  lambda a not inspect isroutine a     gt  gt  gt   a for a in attributes if not a 0  startswith       and a 0  endswith            a    34      b    12         and the more complicated of which can include special attribute name checks or even metaclasses

User · Answer

two function   def get class attr Cls  - gt          import re     return  a for a  v in Cls   dict   items                 if not re match   lt function    gt    str v                 and not  a startswith       and a endswith          def get class attr val cls       attr   get class attr type cls       attr dict          for a in attr          attr dict a    getattr cls  a      return attr dict   use    gt  gt  gt  class MyClass      a    12      b    34      def myfunc self           return self a   gt  gt  gt  m   MyClass    gt  gt  gt  get class attr val m    a    12    b    34

[python] Getting attributes of a class

Python 2 & 3, whitout imports, filtering objects by their address

Solutions in short:

Not filtering objects

Solution in long

Try by yourself

Examples related to python

Examples related to python-2.7

Examples related to class

Examples related to attributes