Iterate over object attributes in python

Question

I have a python object with several attributes and methods   I want to iterate over object attributes     class my python obj object       attr1  a      attr2  b      attr3  c       def method1 self  etc  etc            Statements   I want to generate a dictionary containing all of the objects attributes and their current values  but I want to do it in a dynamic way  so if later I add another attribute I don t have to remember to update my function as well    In php variables can be used as keys  but objects in python are unsuscriptable and if I use the dot notation for this it creates a new attribute with the name of my var  which is not my intent   Just to make things clearer   def to dict self          this is what I already have        d        d  attr1    self attr1     d  attr2    self attr2     d  attr3    self attr3     return d       def to dict self          this is what I want to do        d        for v in my python obj attributes          d v    self v     return d   Update  With attributes I mean only the variables of this object  not the methods

User · Answer

For python 3 6  class SomeClass       def attr list self  should print False            items   self   dict   items           if should print               print f attribute   k     value   v    for k  v in items           return items

User · Answer

Assuming you have a class such as   gt  gt  gt  class Cls object           foo   1         bar    hello          def func self               return  call me       gt  gt  gt  obj   Cls     calling dir on the object gives you back all the attributes of that object  including python special attributes  Although some object attributes are callable  such as methods    gt  gt  gt  dir obj      class        delattr        dict        doc        format        getattribute        hash        init        module        new        reduce        reduce ex        repr        setattr        sizeof        str        subclasshook        weakref      bar    foo    func     You can always filter out the special methods by using a list comprehension    gt  gt  gt   a for a in dir obj  if not a startswith          bar    foo    func     or if you prefer map filters    gt  gt  gt  filter lambda a  not a startswith        dir obj     bar    foo    func     If you want to filter out the methods  you can use the builtin callable as a check    gt  gt  gt   a for a in dir obj  if not a startswith       and not callable getattr obj  a      bar    foo     You could also inspect the difference between your class and its instance object using    gt  gt  gt  set dir Cls   - set dir object   set     module      bar    func      dict      foo      weakref

User · Answer

class someclass          x 1         y 2         z 3         def   init   self              self current idx   0            self items     x   y   z           def next self               if self current idx  lt  len self items                   self current idx    1                 k   self items self current idx-1                  return  k getattr self k               else                  raise StopIteration         def   iter   self              return self   then just call it as an iterable  s someclass   for k v in s      print k     v

User · Answer

For all the pythonian zealots out there I m sure Johan Cleeze would approve of your dogmatism     I m leaving this answer keep demeriting it It actually makes me more confidant  Leave a comment you chickens   For python 3 6  class SomeClass       def attr list1 self  should print False            for k in self   dict   keys                v   self   dict     getitem   k              if should print                  print f attr   k     value   v         def attr list self  should print False            b     k  v  for k  v in self   dict   items            if should print               print f attr   a 0      value   a 1     for a in b          return b

User · Answer

in general put a   iter   method in your class and iterate through the object attributes or put this mixin class in your class   class IterMixin object       def   iter   self           for attr  value in self   dict   iteritems                yield attr  value   Your class    gt  gt  gt  class YourClass IterMixin   pass      gt  gt  gt  yc   YourClass    gt  gt  gt  yc one   range 15   gt  gt  gt  yc two    test   gt  gt  gt  dict yc    one    0  1  2  3  4  5  6  7  8  9  10  11  12  13  14    two    test

User · Answer

Objects in python store their atributes  including functions  in a dict called   dict    You can  but generally shouldn t  use this to access the attributes directly  If you just want a list  you can also call dir obj   which returns an iterable with all the attribute names  which you could then pass to getattr   However  needing to do anything with the names of the variables is usually bad design  Why not keep them in a collection   class Foo object       def   init   self    values           self special values   values   You can then iterate over the keys with for key in obj special values

User · Answer

As mentioned in some of the answers comments already  Python objects already store a dictionary of their attributes  methods aren t included   This can be accessed as   dict    but the better way is to use vars  the output is the same  though   Note that modifying this dictionary will modify the attributes on the instance  This can be useful  but also means you should be careful with how you use this dictionary  Here s a quick example   class A        def   init   self  x 3  y 2  z 5           self x   x         self  y   y         self   z     z      def f self           pass  a   A   print vars a       x   3    y   2     z     5    all of the attributes of  a  but no methods     note how the dictionary is always up-to-date a x   10 print vars a       x   10    y   2     z     5     modifying the dictionary modifies the instance attribute vars a    y     20 print vars a       x   10    y   20     z     5    Using dir a  is an odd  if not outright bad  approach to this problem  It s good if you really needed to iterate over all attributes and methods of the class  including the special methods like   init     However  this doesn t seem to be what you want  and even the accepted answer goes about this poorly by applying some brittle filtering to try to remove methods and leave just the attributes  you can see how this would fail for the class A defined above    using   dict   has been done in a couple of answers  but they all define unnecessary methods instead of using it directly  Only a comment suggests to use vars

User · Answer

The correct answer to this is that you shouldn t  If you want this type of thing either just use a dict  or you ll need to explicitly add attributes to some container  You can automate that by learning about decorators   In particular  by the way  method1 in your example is just as good of an attribute

[python] Iterate over object attributes in python

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