KnowCardPython · OOP: Properties, Methods & Data Classes
Which magic methods make -obj, abs(obj), and ~obj work on your class?
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More in OOP: Properties, Methods & Data Classes
What does this print?
```
class C:
@property
def area(self):
return self.w * self.h
c = C(); c.w, c.h = 3, 4
print(c.area)
print(c.area())
```
You expose a public attribute obj.temp and ship it. Later you need to reject negative values on write. Why is starting with @property from day one the safer call?
A class has @property def x with only a getter. What happens at obj.x = 5?
What does this print?
```
class A:
@staticmethod
def add(a, b):
return a + b
print(A.add(2, 3))
print(A().add(2, 3))
```
What is printed?
```
class A:
@classmethod
def who(cls):
return cls.__name__
class B(A): pass
print(A.who(), B.who())
```
You want Date.from_string("2026-06-27") to build and return a Date instance (an alternative constructor). Which method kind, and what's the key line in the body?
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