Step 3 / Select topic Python Hard

What this bank covers

• C3 linearization
• asyncio concurrency model
• functools.lru_cache
• The GIL
• Small integer interning
• __getattr__ vs __getattribute__
• Assignment expressions (PEP 572)
• Metaclass instantiation order
• Generators as coroutines
• __slots__
• GIL release around blocking calls
• multiprocessing sidesteps the GIL
• __slots__ only helps end to end
• __weakref__ must be an explicit slot
• Metaclass __call__ intercepts instantiation
• type() as a dynamic class factory
• __init_subclass__ hook
• __set_name__
• The descriptor protocol
• Data descriptors override instance __dict__
• property as a descriptor
• Non-data descriptors lose to instance __dict__
• Cooperative super() calls
• How bare super() finds its class
• __new__ owns construction of immutables
• __init__ only runs for matching types
• Singleton via __new__
• Dead weak references return None
• WeakValueDictionary as a non-owning cache
• Cyclic garbage collector
• Generational garbage collection
• __del__ and cyclic collection
• __class_getitem__ for subscriptable classes
• Lock vs RLock reentrancy
• Task cancellation semantics
• Single-dispatch generic functions
• functools.cache
• Coroutine objects are lazy
• Blocking calls stall the whole event loop
• asyncio.sleep(0) as a cooperative yield
• Async generators
• Locks still matter in cooperative concurrency
• await as sugar over yield from
• Generator return values
• contextvars for per-task state
• The GIL protects bytecode instructions, not statements
• String literal interning
• Explicit interning
• Explicit GIL release in C extensions
• Floats are not interned
• ExceptionGroup and except*
• The __prepare__ hook
• fork vs spawn start methods
• Overriding __eq__ nukes the default __hash__
• The hash-invariance contract
• sys.exc_info() outside exception handling
• Virtual subclassing
• Structural ABCs via __subclasshook__
• Iterators are their own __iter__
• cached_property needs an instance __dict__
• Making objects callable
• The __getattribute__ recursion trap
• Immutable C-level types resist monkeypatching
• autospec catches signature drift
• Instance-level vs class-level patching scope
• sys.setrecursionlimit
• No tail-call optimization in CPython
• memoryview and the buffer protocol
• The bytes-like type family
• Customizing pickling with __reduce__
• Customizing deepcopy
• The memo dict prevents infinite recursion
• multiprocessing needs picklable targets
• Explicit shared memory for multiprocessing
• Exact __exit__ suppression semantics
• contextlib.suppress
• __index__ vs __int__
• __exit__ is not called if __enter__ fails
• finally always runs
• __subclasses__() and weak tracking
• finally exceptions override in-flight ones
• The __format__ protocol
• Mutable class attributes are shared state
• Metaclass conflicts
• Stacking @property with @abstractmethod
• The reflected operator fallback protocol
• NotImplemented lets the other side try
• contextlib.ExitStack for dynamic context managers
• Enum value aliasing
• dataclass frozen + hash generation
• Dataclasses reject mutable defaults outright
• array module vs list memory layout
• Double-underscore name mangling
• getrefcount includes its own temporary reference
• id() uniqueness only holds for live objects
• match/case pattern specificity and ordering
• Iterators cannot be rewound
• gc.freeze() and copy-on-write friendliness
• Truthiness fallback chain
• staticmethod and classmethod as descriptors
• Late-binding closures
• Iterators can be consumed only once
• Sort keys instead of comparison functions
• Building bytes: join versus +=