Manipulate data efficiently in Python

Q: How do I practice SQL interview questions?

PracHub provides an interactive SQL console where you can write and test queries against real database schemas. Get instant feedback and compare your solution with the expected output.

Q: What difficulty level is this coding question?

This is a medium difficulty Data Manipulation (SQL/Python) question, commonly asked during Onsite rounds.

Q: What role is this question designed for?

This question is commonly asked for Data Scientist candidates during technical interviews.

Question

Answer the following: (a) Contrast list comprehensions and generators with respect to memory and evaluation; write a generator that yields rolling windows of size k over a list. (b) In CPython 3.x, what is the maximum integer value and why? (c) Demonstrate a bug caused by Python’s pass-by-object-reference when mutating a list argument inside a function; fix it. (d) Given a pandas DataFrame of the events table (columns: user_id, event_date, event_type, revenue), compute per-country 7-day conversion on 2025-09-01 and total revenue using idiomatic groupby and boolean indexing; avoid apply for row-wise operations.

PracHub · Accepted Answer

This question evaluates proficiency in Python data manipulation, including memory and evaluation differences between list comprehensions and generators, CPython integer semantics, mutable argument behavior, and idiomatic pandas groupby and boolean indexing, and is commonly asked to assess performance awareness, understanding of language internals, debugging of mutable state, and practical data-aggregation skills. It belongs to the Data Manipulation (SQL/Python) domain and tests both conceptual understanding of language semantics and practical application of Python and pandas for efficient data processing.

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Manipulate data efficiently in Python