Abdur-Rahmaan Janhangeer

Posted on Feb 15, 2019

Using Python Functions As Classes

#python #trick #oop

In Python, you can use functions as classes. In py, everything is an object. How? I'm no py expert. Here's how we do it!

An Innocent Python Function

a function is like that



def devdotto():
    pass

and a class is like that:



class Car:
    def __init__(self):
        self.wheel = 4
        self.make = 'BWM' # i know

    def move(self):
        print('moving')

more info:

make and wheels are attributes
while move is a method

some tests



car = Car()

print(car.wheel)
print(car.make)

car.move()

gives out



4
BWM
moving

Now Let Us Add Attributes

adding attributes to functions



devdotto.name = 'dev.to'
devdotto.users = 1123234

testing



print(devdotto.name)
print(devdotto.users)

gives out



dev.to
1123234

More Craziness: Adding Methods To Functions

adding an add method:



devdotto.add = lambda x,y: x+y

some info:

testing



print(devdotto.add(1,2))

gives out

Conclusion

Since some one liner libs make use of IEF (Immediately Executed Functions) using lambdas to compile even loops, these can be useful, but i can't think of any use cases (for using functions as classes), this said, this is one of py's party tricks, hence the cover image.

img credit: Photo by Jason Leung on Unsplash

Any ideas? Comment them out below!

Top comments (13)

Dimitri Merejkowsky • Feb 15 '19

Nice one :)

By the way you can turn classes into functions too:

class Foo:
    def __call__(self, a):
        print(f"Calling with a=", a)

foo = Foo()
foo(42)

Valentin Berlier • Feb 15 '19

By the way you can do this:

In [1]: return_hello = lambda *args, **kwargs: 'hello'                   

In [2]: class Foo(metaclass=return_hello): ...                           

In [3]: Foo                                                              
Out[3]: 'hello'

Abdur-Rahmaan Janhangeer • Feb 15 '19

Great! That's the needed comment to complement this article!

Jan Wedel • Feb 15 '19 • Edited

I‘ve written a Python interpreter in Java once where I learned that really everything is an object in python.

I usually ask in job interviews „what’s the difference between Java and Python“ and most candidates say „Java is object-oriented and Python is a scripting language“ :)

Abdur-Rahmaan Janhangeer • Feb 16 '19

you are in language making? really awesome!

Jan Wedel • Feb 16 '19

Oh no, I only wrote an interpreter that executed precompiled Python code! I did this once as a PoC to run Python on an embedded device. It worked but unfortunately as you might imagine, interpreting Python Byte code in Java which was also interpreted byte code on a slow embedded device was terrible slow.

The point is: I learned how beautifully Python is designed internally.
As you stated: everything’s an object

numbers, strings
methods
classes
modules
code blocks

This is truly amazing!

Abdur-Rahmaan Janhangeer • Feb 16 '19

hum ok, embedded programming is another level for me ^{^_}

Ondrej • Feb 15 '19

I don't know Abdur.
I understand that you can utilize OOP principles in Python, but if I really want to do OOP AND the scripting lvl I would rather choose Ruby as my language to go. I just hate Python OOP syntax and things associated with the OOP paradigm in Python. Of course, at the end it will work, but I'm really happy to write my scripts without overhead of using OOP in this particular language.
Thanks for the post though, it was good & inspirational :)