PCAP-31-03 4.2 Employ Class and Object Properties PCAP-31 Practice Questions (Page 3)

Questions 11–15

1. 11expert · hard

   A developer defines `class A: def __init__(self): self.__x = 1` and `class B(A): def __init__(self): super().__init__(); self.__x = 2`. After `b = B()`, what keys exist in `b.__dict__`?

   • A`{'_B__x': 2}`
   • B`{'__x': 1, '__x': 2}`
   • C`{'_A__x': 2}`
   • D`{'_A__x': 1, '_B__x': 2}`
   Reveal Solution Discussion Select an answer first
2. 12expert · hard

   A class `Database` defines `__connection = None` as a class variable. A subclass `MySQLDatabase(Database)` attempts to access `self.__connection` inside its own method. What happens?

   • AIt creates a new class variable `_MySQLDatabase__connection` in the subclass
   • BIt raises a SyntaxError because private class variables cannot be accessed in subclasses
   • CAttributeError, because `__connection` is mangled to `_Database__connection`, not `_MySQLDatabase__connection`
   • DIt successfully accesses the parent's class variable
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4. 13application · medium

   A developer inspects an object's `__dict__` and sees the key `_BankAccount__pin`. What does this indicate about the original attribute definition?

   • AThe class defined an instance variable named `__pin`
   • BThe attribute is a method, not a variable
   • CThe class defined a class variable named `_pin`
   • DThe instance was created outside the class using `obj._pin = ...`
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5. 14expert · hard

   A developer needs to serialize an object's state for debugging. The object has both public instance variables and private ones (defined with double underscores). Which approach reliably captures all instance-level data?

   • ACall `vars(type(obj))` and merge with `obj.__class__.__dict__`
   • BAccess each attribute via `getattr(obj, name)` for names in `type(obj).__dict__`
   • CInspect `obj.__dict__` and include all keys, including mangled private names
   • DUse `dir(obj)` and filter out names starting with an underscore
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6. 15foundation · easy

   What is the key characteristic of a class variable?

   • AIt is automatically deleted when the last instance is deleted
   • BIt is unique to each instance of the class
   • CIt can only be accessed within the class definition
   • DIt is shared among all instances of the class
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