Python में self क्या है? Class Examples के साथ समझें

What is self?

class Student:
    def __init__(self, name, marks):
        self.name  = name      # THIS object's name
        self.marks = marks     # THIS object's marks

    def show(self):
        print(self.name, "scored", self.marks)

s1 = Student("Aman", 92)
s2 = Student("Priya", 88)

s1.show()    # self = s1 here
s2.show()    # self = s2 here

Same show() method, different output — because self pointed to a different object each time.

What Python does behind the scenes

s1.show()
# Python internally converts this to:
Student.show(s1)      # s1 is passed as self automatically

This is the whole secret: the object before the dot is automatically passed as the first argument. That first parameter must be there to receive it, and by convention we name it self.

What happens if you forget self?

class Student:
    def show():              # self missing!
        print("Hello")

s = Student()
s.show()
# TypeError: Student.show() takes 0 positional arguments
# but 1 was given

self.name vs name — the crucial difference

class Student:
    def __init__(self, name):
        self.name = name    # object variable: lives with the object
        name = "temp"       # local variable: dies when __init__ ends

    def greet(self):
        print("Hello", self.name)   # works
        # print(name)               # NameError: name not defined

s = Student("Aman")
s.greet()

self.name is stored inside the object and survives across methods. Plain name is a temporary local variable.

3 facts to say in interviews

• self is not a keyword — you could write def show(this): and use this.name. It works, but the convention is always self.
• self must be the first parameter of every instance method.
• You never pass self yourself — Python passes the object automatically when you call obj.method().