Understanding Python Class and Object

Question

If I have this code:

class Fish(object):
    pass
class Salmon(Fish):
    pass

Is Salmon a object from class Fish? Which one is instance? What is x = Salmon() called?

MSeifert · Accepted Answer · 2017-06-21 09:12:20Z

2

Let me start simple: In Python everything is an object.

But I guess you're confusing "object from class" (I guess you meant "instance of class" there?) with "inheritance":

class Fish(object):
    pass

Creates a class Fish that inherits from object. Likewise:

class Salmon(Fish):
    pass

creates a class Salmon that inherits from Fish.

Both aren't "instances" in the normal sense. They are in fact "instances": they are both instances of type (which in turn subclasses object) the base metaclass for all classes but that's probably a bit too much to go into. Checkout metaclasses in Python if you want to know more.

What actually creates an instance is x = Salmon(): This creates an instance of Salmon.

edited Jun 21, 2017 at 9:12

answered Jun 21, 2017 at 9:06

MSeifert

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2 Comments

Teofanus Gary Over a year ago

Thx dude I get it now!!

MSeifert Over a year ago

@TeofanusGary No problem. Please don't forget to upvote all helpful answers and to accept the most helpful one.

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