CODEWITHSUNDEEP
pythonclassobjectvariablesinit
Tool
Tool

Reputation: 17

Normal variables declared under __init__

In the example seen below, I have declared an object, obj1, using my class, Classy. When obj1 is initialized, I declare a variable using self.var and I have an instance object that I can print to the console. All straight forward.

My question is around the other variable I have set, named variable. Running my code produces no errors, but I have (seemingly) no way of accessing it. It is neither a class variable of Classy, nor an instance variable is obj1.

Where is variable?

class Classy:

    def __init__(self, value):
        self.var = value
        variable = 1


obj1 = Classy("object")
print(obj1.var)

object

Upvotes: 1

Views: 813

Answers (3)

DANIEL ROSSI
DANIEL ROSSI

Reputation: 11

The attribute "variable" is a local attribute that you can only access inside of the __init__() method. Indeed if you modify your class adding "print(locals)"

class classy:

def __init__(self,value):
    self.var = value
    variable = 1
    print(locals())

you can see that this attribute exists inside of the method. But if you get an instance of your class and then write

c = classy(10)
print(c.__dict__)

or

print(dir(c))

you can see that "variable" is not declared in the instance scope. So, "variable" is still a dynamic attribute because you wrote it inside of a method (it is not static) but the difference between it and "var" is that you can only use "variable" inside of init() method.

You can try to write

class classy:
    
    def __init__(self,value):
        self.var = value
        variable = 1
        
    def __increment__(self):
        self.var +=variable

c = classy(10)
c.__increment__() # NameError: name 'variable' is not defined

and see that you can neither use it inside of another method in the same class.

Upvotes: 1

dkhara
dkhara

Reputation: 715

Your variable named variable is a local variable. Specifically, it's local to the __init__() method. You won't be able to access it outside of that method. You can only access it inside of the method. Local variables created inside of the __init__() method really only serve the purpose of creating other instance variables:

class Classy:

    def __init__(self, value):
        self.var = value
        variable = 1
        self.new_var = variable + 1 # new_var is 2


obj1 = Classy("object")
print(obj1.var)

Upvotes: 3

LhasaDad
LhasaDad

Reputation: 2153

the variable variable is scoped to the function. when you return from the function it is gone.

Upvotes: 1

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