JuniorTheoryCommon

What does the program print?

Python

class Counter:
    def __init__(self):
        self.value = 0

    def add(self, n):
        self.value += n


a = Counter()
b = Counter()
a.add(5)
print(a.value, b.value)

5 0

Expecting 5 5, as if both objects shared one value: each call Counter() runs __init__ for a new instance, and self.value belongs to that instance alone.
Expecting a TypeError because add has two parameters and gets one argument: Python passes the instance as self itself, so a.add(5) fills both.

What would b.add(2) followed by print(a.value, b.value) print?
How does self inside add know which object to change?

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JuniorTheoryCommon

What does the program print?

Python

class Counter:
    def __init__(self):
        self.value = 0

    def add(self, n):
        self.value += n


a = Counter()
b = Counter()
a.add(5)
print(a.value, b.value)

5 0

Expecting 5 5, as if both objects shared one value: each call Counter() runs __init__ for a new instance, and self.value belongs to that instance alone.
Expecting a TypeError because add has two parameters and gets one argument: Python passes the instance as self itself, so a.add(5) fills both.

What would b.add(2) followed by print(a.value, b.value) print?
How does self inside add know which object to change?

Back to questions Open topic in roadmap →Answer it yourself — Quiz