PCPP1 Practice Test 5 — 10 Questions

Question 1

When implementing secure coding practices in a web-facing Python application, how should you handle raw user input to prevent command injection?

Accepted Answer

Pass input arguments as a list to subprocess.run(args, shell=False).. Using the 'subprocess' module with 'shell=False' (the default) prevents the shell from interpreting user-provided strings as commands.

Answer

Pass the entire input string to os.system().

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Concatenate the input string into a shell command for execution.

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Sanitize input using a custom regex to remove special characters.

Question 2

Which TWO of these identify a potential 'code smell' in Python exception handling?

Accepted Answer

Swallowing exceptions with an empty 'except' block.. Swallowing exceptions and catching BaseException are both poor practices.

Answer

Using 'finally' for cleanup.

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Catching specific exceptions.

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Raising custom exceptions.

Question 3

What is the result of applying the @staticmethod decorator to a method inside a class that also defines a metaclass?

Accepted Answer

The method is correctly bound as a static function regardless of the metaclass.. The @staticmethod decorator creates a static method object which is stored in the class dictionary; it is independent of the metaclass's __init__ logic for instance methods.

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The metaclass must manually convert it back to a static method.

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It raises a TypeError at class definition time.

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The metaclass will treat the method as an instance method.

Question 4

Which magic method allows an object to behave like a function?

Accepted Answer

__call__. The __call__ method enables an object to be invoked with parentheses syntax.

Answer

__apply__

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__invoke__

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__func__

Question 5

What is the purpose of the 'type' function when called with three arguments?

Accepted Answer

To create a new class dynamically.. It is used for dynamic class creation: type(name, bases, dict).

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To register a class.

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To inherit from multiple classes.

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To check object type.

Question 6

What is the purpose of the __repr__ method?

Accepted Answer

Unambiguous representation for debugging.. It provides a formal, unambiguous string representation of an object, ideally suitable for re-creating the object.

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To be called by print().

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User-friendly output.

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To store the object in memory.

Question 7

When using abstract base classes (ABCs) from the abc module, what happens if a class inherits from an ABC but fails to implement one of the abstract methods?

Accepted Answer

The class will be marked as abstract and will raise a TypeError upon instantiation.. Python will raise a TypeError when you attempt to instantiate the class, preventing the creation of an incomplete object.

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The class will be created, but calling the missing method will raise an AttributeError.

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The missing method will default to a 'pass' statement.

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The parent ABC will automatically provide a NotImplementedError.

Question 8

When implementing the Singleton pattern, what is the advantage of using a module-level instance over a class-based Singleton?

Accepted Answer

It is simpler and leverages Python's built-in module caching mechanism.. Python modules are naturally Singletons because they are initialized only once upon the first import.

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It is more secure.

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It allows multiple instances if needed.

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It supports lazy loading.

Question 9

Which method is used to customize the behavior of the 'in' operator?

Accepted Answer

__contains__. The __contains__ method is called when using the 'in' or 'not in' operators.

Answer

__has__

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__find__

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__in__

Question 10

When using the __call__ method to implement a decorator, what does the decorator receive as an argument?

Accepted Answer

The function to be decorated.. The decorator receives the function object that is being decorated as the argument to the constructor (if the decorator is a class instance) or directly if it is a function.

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The arguments to the function.

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The instance of the class.

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The class object.