looping over all member variables of a class in python

Question

How do you get a list of all variables in a class thats iteratable? Kind of like locals(), but for a class

class Example(object):
    bool143 = True
    bool2 = True
    blah = False
    foo = True
    foobar2000 = False

    def as_list(self)
       ret = []
       for field in XXX:
           if getattr(self, field):
               ret.append(field)
       return ",".join(ret)

this should return

>>> e = Example()
>>> e.as_list()
bool143, bool2, foo

Why can't use use `for field in [ self.bool143, self.bool2, self.blah, self.foo, self.foobar2000 ]`? How does it happen that you don't know the instance variables of the class? — S.Lott, Sep 09 '09 at 11:52
S.Lott: thats what I ended up doing anyways. In my real code, I have like 40 variables, and I thought it'd be better and more DRY to not have to manually make the iteration list. — priestc, Sep 10 '09 at 01:43
Possible duplicate of [Iterate over object attributes in python](https://stackoverflow.com/questions/11637293/iterate-over-object-attributes-in-python) — Trevor Boyd Smith, Nov 09 '17 at 16:09
Related: [python - Is there a built-in function to print all the current properties and values of an object? - Stack Overflow](https://stackoverflow.com/questions/192109/is-there-a-built-in-function-to-print-all-the-current-properties-and-values-of-a) — user202729, Feb 04 '21 at 00:11
`ClassName.__dict__["__doc__"]` This will filter out functions, in-built variables etc. and give you just the fields that you need! — Hyuga Hinata, Aug 24 '21 at 02:04

mthurlin · Accepted Answer · 2017-02-16T15:54:01.230

188

dir(obj)

gives you all attributes of the object. You need to filter out the members from methods etc yourself:

class Example(object):
    bool143 = True
    bool2 = True
    blah = False
    foo = True
    foobar2000 = False

example = Example()
members = [attr for attr in dir(example) if not callable(getattr(example, attr)) and not attr.startswith("__")]
print members

Will give you:

['blah', 'bool143', 'bool2', 'foo', 'foobar2000']

edited Feb 16 '17 at 15:54

answered Sep 09 '09 at 07:23

mthurlin

25,019
4
37
46

10

why instantiate an object: dir(Example()) instead of just the class type dir(Example) – Erdal Apr 30 '11 at 22:53
2

because I'm guessing the OP is looking for instance variables (which might not be present in the class). – mthurlin May 15 '11 at 17:57
9

and how do you get the values? – knutole Jan 18 '13 at 08:20
8

@knutole: getattr(object, attr) – opello Jan 13 '14 at 15:36
8

How does `callable(attr)` work? Isn't `attr` a string? – cubuspl42 Jul 08 '14 at 10:37
7

you should have used `vars(Example).items()` or `vars(instance.__class__).items()` instead of `dir()` if you want to check if its callable or not because dir will only return '`string`s as names.. – rrw Mar 26 '16 at 16:44
1

truppo, please update your answer, see below answer about why callable(attr) doesn't work – ikku100 Jan 26 '17 at 13:41
`ClassName.__dict__["__doc__"]` This will filter out functions, in-built variables etc. and give you just the fields that you need! – Hyuga Hinata Aug 24 '21 at 02:04

score 152 · Answer 2 · answered Nov 08 '12 at 10:10

152

If you want only the variables (without functions) use:

vars(your_object)

answered Nov 08 '12 at 10:10

Nimo

7,826
5
37
40

5

You still need to filter __vars__ but this is the correct answer – gaborous Aug 10 '14 at 20:16
3

really like this approach gonna use it to find out what to serialise before sending states over network for instance... – Thom Apr 13 '15 at 11:17
13

`vars` does *not* include the class variables, only the instance variables. – DilithiumMatrix Apr 10 '16 at 20:24
To add to your answer, specifying `vars(self)['_data']` should give you only the variables back. – MikeyE Feb 07 '17 at 08:01
2

@DilithiumMatrix you need to use vars(THECLASSITSELF) on the class itself to get class variables. Check my answer below. – AmirHossein Aug 23 '17 at 08:15
Thank you for this! I like readability and the pprint() version I found here: https://stackoverflow.com/a/193539/1896134 – JayRizzo Oct 19 '18 at 02:29
2

Using this method to specifically answer the OP's question: `members = list(vars(example).keys())` as (at least in python3) `vars` returns a `dict` mapping the name of the member variable to it's value. – Michael Hall Aug 21 '19 at 10:59
`ClassName.__dict__["__doc__"]` This will filter out functions, in-built variables etc. and give you just the fields that you need! – Hyuga Hinata Aug 24 '21 at 02:04

score 31 · Answer 3 · edited Jan 11 '13 at 10:47

31

@truppo: your answer is almost correct, but callable will always return false since you're just passing in a string. You need something like the following:

[attr for attr in dir(obj()) if not callable(getattr(obj(),attr)) and not attr.startswith("__")]

which will filter out functions

edited Jan 11 '13 at 10:47

Trent

2,286
2
32
47

answered Dec 21 '09 at 10:14

user235925

818
1
8
11

`ClassName.__dict__["__doc__"]` This will filter out functions, in-built variables etc. and give you just the fields that you need! – Hyuga Hinata Aug 24 '21 at 02:05

score 6 · Answer 4 · answered Sep 09 '09 at 07:21

6

>>> a = Example()
>>> dir(a)
['__class__', '__delattr__', '__doc__', '__format__', '__getattribute__', '__hash__',
'__init__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__',
'__sizeof__', '__str__', '__subclasshook__', 'bool143', 'bool2', 'blah',
'foo', 'foobar2000', 'as_list']

—as you see, that gives you all attributes, so you'll have to filter out a little bit. But basically, dir() is what you're looking for.

answered Sep 09 '09 at 07:21

balpha

48,271
17
112
129

`ClassName.__dict__["__doc__"]` This will filter out functions, in-built variables etc. and give you just the fields that you need! – Hyuga Hinata Aug 24 '21 at 02:05

score 1 · Answer 5 · answered Jun 25 '21 at 07:10

1

Similar to vars(), one can use the below code to list all class attributes. It is equivalent to vars(example).keys().

example.__dict__.keys()

answered Jun 25 '21 at 07:10

Mehdi

634
8
7

`ClassName.__dict__["__doc__"]` This will filter out functions, in-built variables etc. and give you just the fields that you need! – Hyuga Hinata Aug 24 '21 at 02:05

score 0 · Answer 6 · answered Aug 24 '21 at 02:01

0

ClassName.__dict__["__doc__"]

This will filter out functions, in-built variables etc. and give you just the fields that you need!

answered Aug 24 '21 at 02:01

Hyuga Hinata

49
8

score -1 · Answer 7 · edited Aug 08 '19 at 04:39

-1

row2dict = lambda r: {c.name: str(getattr(r, c.name)) for c in r.__table__.columns} if r else {}

Use this.

edited Aug 08 '19 at 04:39

4b0

20,627
30
92
137

answered Aug 08 '19 at 04:37

user1825586

1

Misleading. There's no attribute '__table__' in classes by default. – ben26941 May 04 '20 at 13:50
`ClassName.__dict__["__doc__"]` This will filter out functions, in-built variables etc. and give you just the fields that you need! – Hyuga Hinata Aug 24 '21 at 02:05

Abhijeet Pandey · Answer 8 · 2017-07-15T02:33:29.450

-2

    class Employee:
    '''
    This class creates class employee with three attributes 
    and one function or method
    '''

    def __init__(self, first, last, salary):
        self.first = first
        self.last = last
        self.salary = salary

    def fullname(self):
        fullname=self.first + ' ' + self.last
        return fullname

emp1 = Employee('Abhijeet', 'Pandey', 20000)
emp2 = Employee('John', 'Smith', 50000)

print('To get attributes of an instance', set(dir(emp1))-set(dir(Employee))) # you can now loop over

edited Jul 15 '17 at 02:33

answered Jul 15 '17 at 02:28

Abhijeet Pandey

1
2

`ClassName.__dict__["__doc__"]` This will filter out functions, in-built variables etc. and give you just the fields that you need! – Hyuga Hinata Aug 24 '21 at 02:05

score -4 · Answer 9 · answered Sep 09 '09 at 09:57

-4

The easy way to do this is to save all instances of the class in a list.

a = Example()
b = Example()
all_examples = [ a, b ]

Objects don't spring into existence spontaneously. Some part of your program created them for a reason. The creation is done for a reason. Collecting them in a list can also be done for a reason.

If you use a factory, you can do this.

class ExampleFactory( object ):
    def __init__( self ):
        self.all_examples= []
    def __call__( self, *args, **kw ):
        e = Example( *args, **kw )
        self.all_examples.append( e )
        return e
    def all( self ):
        return all_examples

makeExample= ExampleFactory()
a = makeExample()
b = makeExample()
for i in makeExample.all():
    print i

answered Sep 09 '09 at 09:57

S.Lott

373,146
78
498
766

I like the idea (I might actually use that in a current project). It's not an answer to the question, though: The OP wants to list the attributes, not the instances themselves. – balpha Sep 09 '09 at 10:51
@balpha: Ooops. Didn't read the question. 90% of the time, it's a duplicate of "how do I find all instances of a class." The actual question (now that you point it out) isn't sensible. You know the instance variables, just make a list. – S.Lott Sep 09 '09 at 11:51
`ClassName.__dict__["__doc__"]` This will filter out functions, in-built variables etc. and give you just the fields that you need! – Hyuga Hinata Aug 24 '21 at 02:06

looping over all member variables of a class in python

9 Answers9

Linked

Related