Print all properties of a Python Class [duplicate]

Question

I have a class Animal with several properties like:

class Animal(object):
    def __init__(self):
        self.legs = 2
        self.name = 'Dog'
        self.color= 'Spotted'
        self.smell= 'Alot'
        self.age  = 10
        self.kids = 0
        #many more...

I now want to print all these properties to a text file. The ugly way I'm doing it now is like:

animal=Animal()
output = 'legs:%d, name:%s, color:%s, smell:%s, age:%d, kids:%d' % (animal.legs, animal.name, animal.color, animal.smell, animal.age, animal.kids,)

Is there a better Pythonic way to do this?

Archambault

Did you try searching for questions related to locating all properties of a class? It's been asked. #1215908 for example. – Outbid

@S.Lott: Although the OP asked specifically about properties of a class, from their example code I think it's fairly obvious they're not taking about data descriptors. – Moving

Relevant: #1398522 – Jerold

Python offers the vars() function which returns a 'dictionary' of all the instance attributes along with their values. It is similar to the above methods, the only difference being, vars() focuses only on instance attributes and also returns their values along with them. – Moorefield

these are attributes of an instance, not a class – Botulin

Answer 1

In this simple case you can use vars():

an = Animal()
attrs = vars(an)
# {'kids': 0, 'name': 'Dog', 'color': 'Spotted', 'age': 10, 'legs': 2, 'smell': 'Alot'}
# now dump this in some way or another
print(', '.join("%s: %s" % item for item in attrs.items()))

If you want to store Python objects on the disk you should look at shelve — Python object persistence.

Churchyard

Oh nice, never used vars like that! I thought it just acted like locals(), didn't know you could use it on a class/module. Very useful! – Havildar

vars only works if you are using __dict__ to store the attributes (which is the default behaviour for Python objects). Refer to @BasicWolf's answer if you are using __slots__ – Preterit

Note that in this way you get unordered results. If you need to print for example in order of declaration, and you do not want to do it manually, check this – Cigarillo

How would you use this to print something like: an.name = Dog? I tried the following, does not work. '''f.write('\n'.join(["{}.{} = '{}'".format(myname.name, (k for k in myname.__dict__.keys()),(v for v in myname.__dict__.values()))]))''' – Hent

TypeError: vars() argument must have __dict__ attribute – Karnes

Thanks but the name "BasicWolf" disappeared ... 😅 (possibly because of a renaming). – Vespucci

The second answer was written by someone with a wolf as an avatar. See https://mcmap.net/q/109042/-print-all-properties-of-a-python-class-duplicate – Liberality

Answer 2

Another way is to call the dir() function (see https://docs.python.org/2/library/functions.html#dir).

a = Animal()
dir(a)   
>>>
['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__',
 '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', 
 '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 
 '__weakref__', 'age', 'color', 'kids', 'legs', 'name', 'smell']

Note, that dir() tries to reach any attribute that is possible to reach.

Then you can access the attributes e.g. by filtering with double underscores:

attributes = [attr for attr in dir(a) 
              if not attr.startswith('__')]

This is just an example of what is possible to do with dir(), please check the other answers for proper way of doing this.

Cullin

This is probably the right approach, but it should be pointed out that what it's doing is printing out the attributes, not the things called Properties in new-style classes in Python, and that it's doing it based on an instance of a class, not the class itself (because these attributes don't exist until the class instance is created and __init__() is called). Also if any other attributes are created later, they will be omitted, obviously. – Moving

Indeed. But I bet, it's really hard to teach one the overwhelming power of Python's dynamic constructions (objects, types, meta-classes, classes) unless one face them. – Cullin

A better filtering (by user235925 on #1398522) [attr for attr in dir(a) if not callable(getattr(Animal,attr)) and not attr.startswith("__")] – Concettaconcettina

Works with @property as well – Legist

The only thing that works with PyUNO LibreOffice API. – Susysuter

filter(lambda x: not x.startswith('__'), dir(object)) - for list only filter(lambda x: not x.startswith('__'), object.__dict__) - for dict. For class attributes you will want to access object.__class__ and then dir it or __dict__ – Reg

This is an fast and easy way to inspect any object, since an unfamiliar object may seem like a "dark box", you "unveil" its methods and attributes. – Bullish

Answer 3

Maybe you are looking for something like this?

    >>> class MyTest:
        def __init__ (self):
            self.value = 3
    >>> myobj = MyTest()
    >>> myobj.__dict__
    {'value': 3}

Sophisticated

Note since this gives you a dictionary, you can also just look at the keys if you want a quick API reference print(o.__dict__.keys()). – Nez

Answer 4

try ppretty:

from ppretty import ppretty


class Animal(object):
    def __init__(self):
        self.legs = 2
        self.name = 'Dog'
        self.color= 'Spotted'
        self.smell= 'Alot'
        self.age  = 10
        self.kids = 0


print ppretty(Animal(), seq_length=10)

Output:

__main__.Animal(age = 10, color = 'Spotted', kids = 0, legs = 2, name = 'Dog', smell = 'Alot')

Presentable

Answer 5

Here is full code. The result is exactly what you want.

class Animal(object):
    def __init__(self):
        self.legs = 2
        self.name = 'Dog'
        self.color= 'Spotted'
        self.smell= 'Alot'
        self.age  = 10
        self.kids = 0

if __name__ == '__main__':
    animal = Animal()
    temp = vars(animal)
    for item in temp:
        print item , ' : ' , temp[item]
        #print item , ' : ', temp[item] ,

Headward

Answer 6

Just try beeprint

it prints something like this:

instance(Animal):
    legs: 2,
    name: 'Dog',
    color: 'Spotted',
    smell: 'Alot',
    age: 10,
    kids: 0,

I think is exactly what you need.

Lanyard

If you're a SQLAlchemy user, this doesn't show your object's content properly. – Erosive

@paulochf... please explain... just double checked...we're talking about python here and not SQL.... – Dioxide

If the referred Python class is a SqlAlchemy model, one could want to print all of its attributes. – Erosive