Question 1

Create a Python program to demonstrate the use of set operations (union, intersection).

Accepted Answer

**Ops:** `a|b` union, `a&b` intersection, `a-b` diff, `a^b` sym diff. Methods: `a.union(b)`, `a.intersection(b)`. **Why:** Dedup, overlap, record matching. **Production:** Set-based joins for large datasets....

Question 2

Describe Spark's memory management model. How do you handle heap memory overhead issues?

Accepted Answer

**Model:** Executor split—execution (shuffle, compute) + storage (cache). Off-heap for large. **OOM fixes:** More executor memory; fewer partitions; avoid collect; broadcast small joins; repartition. **Tune:** spark.memory.fraction, storageFraction. **Why:** GC and spill hurt performance....

Question 3

Explain the difference between mutable and immutable objects in Python.

Accepted Answer

**Mutable:** list, dict, set—change in-place. **Immutable:** tuple, str, int—cannot. **Example:** `a.append(3)` vs `t.append(3)` fails. **Hashable:** Immutables as dict keys. **Why:** Thread safety; caching....

Question 4

Explain the differences between multiprocessing and multithreading.

Accepted Answer

**Threading:** Shared memory; GIL limits CPU parallelism. I/O-bound. **Multiprocessing:** Separate processes; true CPU parallelism. CPU-bound. **Python:** threading vs multiprocessing. **Use:** ProcessPoolExecutor CPU; ThreadPoolExecutor I/O. **Why:** GIL....

Question 5

Implement a Python function to count unique words from a file and write them to another file.

Accepted Answer

**Code:** words=set(); for line in open('in.txt'): words.update(line.split()); open('out.txt','w').write('
'.join(sorted(words))). Or Counter. **Why:** Dedup. **Production:** Encoding; large file streaming.

Question 6

Write a decorator function to log the execution time of a function.

Accepted Answer

**Pattern:** Wrap function, time before/after, log. Use functools.wraps to preserve __name__, __doc__. time.perf_counter for wall-clock.

def log_time(func):
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        start = time.perf_counter()
        result = func(*args, **kwargs)
        print(f'{func.__name__}: {time.perf_counter()-start:.3f}s')
        return result
    return wrapper

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