32 questions · Advanced Oop And Performance topic · All types, answers revealed
You are utilizing abstract base classes (ABCs). How do you enforce that a subclass implements a specific method?
@abstractmethod ensures the subclass cannot be instantiated without overriding the method.
Why this answer
The @abstractmethod decorator marks a method as requiring implementation in concrete subclasses.
You need to prevent an object's attribute from being modified after it is set. Which approach provides the most robust implementation?
A @property without a @name.setter makes the attribute read-only.
Why this answer
A property with only a getter (or a custom setter that raises an exception) effectively creates a read-only attribute.
You have an object that behaves like a function. Which magic method must be implemented to make this possible?
__call__ turns an object into a callable.
Why this answer
The __call__ method allows an object instance to be invoked as a function.
You need to ensure that a class can only be instantiated once throughout the application lifecycle. Which design pattern is most appropriate?
Singleton restricts instantiation to a single object.
Why this answer
The Singleton pattern ensures that a class has only one instance and provides a global point of access to it.
When managing resources like file handles, what is the best practice to ensure they are always closed?
The with statement guarantees resource release.
Why this answer
The with statement (context manager) ensures that cleanup code is executed regardless of exceptions.
When using inheritance, how can you explicitly call a method from a specific parent class that is not the immediate superclass?
Direct invocation on the class bypasses the MRO.
Why this answer
Calling the method directly on the class object (e.g., Parent.method(self)) bypasses the MRO.
You need to implement a custom class that behaves like a sequence, allowing indexing and length checking. Which magic methods are required?
These two methods allow indexing and length retrieval.
Why this answer
To be a sequence, a class needs to implement __getitem__ and __len__.
In a multi-threaded application, you need to ensure that shared state is modified safely. Which tool is the most appropriate for this task?
Locks provide mutual exclusion to prevent race conditions.
Why this answer
The threading.Lock primitive allows only one thread to access a resource at a time.
When writing a metaclass, what is the 'cls' parameter in the __new__ method referring to?
The first argument to __new__ in a metaclass is the metaclass type.
Why this answer
In a metaclass's __new__ method, 'cls' refers to the metaclass itself, not the class being created.
Which THREE of the following are features of the 'threading' module in Python?
Semaphores are supported for resource counting.
Why this answer
The threading module provides Locks, Semaphores, and Events for synchronization.
Which operator is used to perform bitwise AND operations?
& performs bitwise AND.
Why this answer
The & operator is the bitwise AND operator in Python.
You are handling large datasets and want to improve memory efficiency. Which Python feature allows you to iterate over a large sequence without loading it entirely into memory?
Generators yield values on demand, saving memory.
Why this answer
Generators provide a lazy evaluation mechanism to yield items one at a time.
Which magic method is used to define how an object is displayed for developers (for debugging)?
__repr__ is for developer-focused, unambiguous representation.
Why this answer
__repr__ is the magic method used to provide an unambiguous string representation of an object.
Which keyword is used to raise an exception in Python?
raise is the correct Python keyword.
Why this answer
The raise keyword is used to trigger an exception.
You are designing a class hierarchy where a subclass needs to ensure it calls the constructor of its parent in a multiple inheritance scenario. Which mechanism is the standard Pythonic approach to handle this dynamically?
super() correctly traverses the MRO, ensuring all classes are initialized only once.
Why this answer
super() is the standard way to delegate to the next class in the Method Resolution Order (MRO).
Which TWO of the following are valid ways to create a generator in Python?
This defines a generator function.
Why this answer
Generators can be created via generator expressions (using parentheses) or generator functions (using the yield keyword).
You need to ensure that a method can be called on the class directly, without requiring an instance. Which decorator should be used?
@classmethod receives the class reference.
Why this answer
The @classmethod decorator receives the class as the first argument, allowing factory-style methods.
Which TWO of the following are true about the 'descriptor protocol' in Python?
This is the core definition of the descriptor protocol.
Why this answer
Descriptors define __get__, __set__, or __delete__, and they allow objects to customize attribute access.
You need to compare two objects for equality based on a custom attribute. Which method should you override?
__eq__ implements the equality operator.
Why this answer
The __eq__ magic method defines the behavior of the equality operator (==).
When writing a context manager using the @contextlib.contextmanager decorator, what should the function do to pass a value to the 'as' clause?
Yielding passes control to the block inside the with statement and provides the value.
Why this answer
The yield statement in a decorated generator function passes the value to the with statement's as target.
You are using 'slots' to save memory. What is a significant side effect of defining __slots__ in a class?
Instances cannot have attributes assigned outside the defined slots.
Why this answer
Classes with __slots__ do not allow the creation of new attributes dynamically unless '__dict__' is explicitly included in __slots__.
You want to store an object in a set. What must the object implement?
These are the requirements for an object to be hashable.
Why this answer
To be hashable (and thus stored in a set), an object must implement __hash__ and have equality defined via __eq__.
You are profiling your code and identify that a specific method is called millions of times. You decide to use a descriptor to optimize attribute access. What must the descriptor implement to intercept attribute assignment?
__set__ allows the descriptor to intercept and handle assignment.
Why this answer
A data descriptor is defined as an object that implements both __get__ and __set__ (or __delete__).
When optimizing Python code, which tool should you use to identify hot spots in the execution path?
cProfile provides deterministic profiling of Python programs.
Why this answer
cProfile is the standard built-in profiler in Python for identifying performance bottlenecks.
Which TWO of the following are Python object-oriented concepts?
Polymorphism allows objects to be treated as instances of their parent class.
Why this answer
Inheritance and Polymorphism are fundamental OOP pillars in Python.
Which THREE of the following are true about Python metaclasses?
In Python, metaclasses are subclasses of 'type'.
Why this answer
Metaclasses are types, they allow modifying class creation, and they are defined by inheriting from 'type'.
You have a performance-critical application using heavy objects. You want to reduce memory footprint by preventing the creation of __dict__ for every instance. How should you proceed?
__slots__ explicitly defines the allowed attributes, saving memory by removing the instance-specific dictionary.
Why this answer
Defining __slots__ in a class prevents the creation of __dict__ and __weakref__ for instances, significantly reducing memory usage.
You need to dynamically add methods to a class at runtime. Which mechanism allows you to modify the class object before it is fully constructed?
Metaclasses control the creation of the class itself.
Why this answer
Metaclasses, specifically the __new__ method, allow for the modification of class creation.
Which built-in function allows you to retrieve an attribute from an object by its string name?
getattr(obj, 'name') returns the value of the attribute.
Why this answer
getattr() is the built-in function to access object attributes dynamically.
Which THREE of the following can be used to improve the performance of a Python application?
Profiling is essential for performance tuning.
Why this answer
Profiling, algorithm optimization, and using built-in C-implemented functions are key strategies.
Which TWO of the following statements about the Python Method Resolution Order (MRO) are true?
__mro__ stores the calculated resolution order.
Why this answer
MRO uses the C3 linearization algorithm and it can be inspected via the __mro__ attribute or the mro() method.
Which THREE of the following are benefits of using __slots__?
Attribute access can be faster due to the structure of slots.
Why this answer
__slots__ reduces memory usage, prevents the creation of __dict__, and can potentially speed up attribute access.
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