Explain decorators with a practical example.
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of Python conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
A decorator is a callable that takes a function and returns a new one, adding behaviour without changing the original code. The @decorator syntax is sugar for func = decorator(func).
import functools, time
def timed(func):
@functools.wraps(func)
def wrapper(*args, **kwargs):
start = time.perf_counter()
result = func(*args, **kwargs)
print(f'{func.__name__} took {time.perf_counter() - start:.3f}s')
return result
return wrapper
@timed
def train():
...
Real uses: logging, authentication, caching, retries, rate limiting. functools.wraps preserves the wrapped function's metadata. Decorators with arguments need an extra layer of nesting.
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.