PCAP-31-03 4.3 Equip a Class with Methods PCAP-31 Practice Questions (Page 9)

Questions 41–45

1. 41expert · medium

   A developer is refactoring a `Report` class. They want to replace a regular function `format_data(data)` with a method `format_data(self, data)` that also uses `self.header`. Which of the following is the primary benefit of making it a method?

   • AThe method can be called without an instance.
   • BThe method does not need a `self` parameter.
   • CThe method can be defined outside the class.
   • DThe method can access and use instance-specific attributes like `self.header`.
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2. 42expert · hard

   A developer is working with a `Timer` class that has a method `start(self)` and a method `stop(self)`. They want to ensure that `stop` can be called only after `start` has been called. Which approach best enforces this constraint?

   • AAdd an instance attribute `self.running` that is set to `True` in `start` and checked in `stop`.
   • BUse a global variable to track the state.
   • CUse a class attribute `running` that is shared across all instances.
   • DRaise an exception in `stop` if `self.running` is not set.
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4. 43expert · hard · select all that apply

   A developer is designing a `User` class with a method `update_profile(self, name, email)`. They want to reuse validation logic from a method `_validate_email(self, email)`. Which of the following statements are true about calling `_validate_email` from `update_profile`? Select all that apply.

   • AYou can call it as `self._validate_email(self, email)`.
   • BYou can call it as `_validate_email(email)`.
   • CYou can call it as `User._validate_email(self, email)`.
   • DYou should call it as `self._validate_email(email)`.
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5. 44application · medium

   In a `ShoppingCart` class, the method `add_item(self, item)` needs to call another method `_update_total(self, price)` to recalculate the total after adding an item. How should `add_item` invoke `_update_total`?

   • A`_update_total(item.price)`
   • B`ShoppingCart._update_total(item.price)`
   • C`self._update_total(item.price)`
   • D`self._update_total(self, item.price)`
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6. 45expert · medium · select all that apply

   A developer is explaining to a colleague why a method must have `self` as its first parameter. Which of the following are valid reasons? Select all that apply.

   • A`self` is optional and can be omitted if the method does not use instance data.
   • B`self` is required to distinguish methods from regular functions.
   • C`self` allows the method to access and modify instance attributes.
   • D`self` allows the method to call other methods on the same instance.
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