CODEWITHSUNDEEP
pythonclass
idlackage
idlackage

Reputation: 2863

Why am I allowed to access a nonexistant variable?

Possibly a dumb question, but I'm more used to Java and the likes and thus don't get why I can do this:

class A:
    def __init__( self ):
        pass

a = A()
a.description = "whyyy"

print a.description

And have it print out whyyy instead of giving me an error.

Upvotes: 0

Views: 56

Answers (2)

Amber
Amber

Reputation: 526723

Because Python objects are dynamic - they aren't required to follow a rigid schema.

Creating an instance of a class gives you an object that already has certain things defined, but you're allowed to dynamically add other things to that instance; you're not restricted to the original class definition.

Upvotes: 2

Samy Arous
Samy Arous

Reputation: 6814

Variables spring into existence by being assigned a value, and they are automatically destroyed when they go out of scope.

For objects, you can add new fields dynamically on runtime. Note that this won't change the class description. Only the current instance.

class A:
    def __init__( self ):
        pass

a = A()
a.description = "whyyy"

print a.description

b = A()

print b.description # Should return an error

Upvotes: 0

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