Performance Optimization Flashcards

Which Python built-in function returns an iterator over a range of numbers without creating a list in memory?

Answer: range()

range() in Python 3 returns a lazy iterator that generates numbers on demand, avoiding memory allocation for the full sequence.

What is the primary advantage of using `array` module over a list for numeric data in Python?

Answer: Lower memory usage due to typed storage

The array module stores elements as typed C values, consuming significantly less memory than Python lists which store object references.

Which caching strategy does `functools.lru_cache` implement?

Answer: Least Recently Used (LRU)

lru_cache evicts the least recently used entries when the cache reaches its maximum size, keeping frequently accessed results.

What does the `__slots__` class attribute do in Python?

Answer: Replaces the instance __dict__ to reduce memory overhead

__slots__ eliminates the per-instance __dict__, reducing memory usage significantly when creating many instances of a class.

Which of the following is the fastest way to concatenate many strings in Python?

Answer: Using ''.join(list_of_strings)

''.join() is O(n) because it allocates one buffer for all strings, while += in a loop creates a new string object on every iteration.

What is the time complexity of checking membership in a Python set compared to a list?

Answer: O(1) for set, O(n) for list

Sets use a hash table internally, giving O(1) average-case membership testing, whereas lists require O(n) linear scan.

What does the `timeit` module measure in Python?

Answer: Execution time of small code snippets

timeit runs a code snippet many times and returns the best elapsed wall-clock time, minimizing measurement noise for micro-benchmarks.