Dataframes Interview Questions

12 real Dataframes questions asked in live technical interviews — each with a model answer. Updated weekly.

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Given two pandas DataFrames, df_employee and df_department, write code to join them on the employee ID, select the default columns, and write the resulting DataFrame back to a file.🟢 Easy · Coding · Asked 1×Write code to join the employee DataFrame with the department DataFrame, include the department commission, and write the result to a CSV file.🟢 Easy · Coding · Asked 1×Given a DataFrame with columns ID and email, generate two additional columns: first name and last name, using the email column. For example, the left side of the dot is the first name, and the right side is the last name.🟡 Medium · Coding · Asked 1×Explain how to perform a left join in PySpark and how broadcast join optimization can be used when the right table is small.🟡 Medium · Conceptual · Asked 1×Can you explain a PySpark transformation you personally developed? What were the input DataFrames? What type of joins did you use? Did you save the input and output as views?🟡 Medium · Coding · Asked 1×Write code to perform a broadcast join between sales data and stores data.🟡 Medium · Coding · Asked 1×Explain how inner and left joins work in Python and provide examples.🟡 Medium · Conceptual · Asked 1×Provide PySpark code to compute the acceptance rate per date based on the given table and code.🟡 Medium · Coding · Asked 1×Need PySpark code to compute acceptance rate per date.🟡 Medium · Coding · Asked 1×Give PySpark code to calculate the friend acceptance rate for each date when friend requests were sent. A request is sent if action = 'sent' and accepted if action = 'accepted'. If a request is not accepted, there is no record of it being accepted in the table. The output should only include dates where requests were sent and at least one of them was accepted (acceptance can occur on any date after the request is sent).🟡 Medium · Coding · Asked 1×How can you compute a cumulative sum (running balance) ordered by date using an unbounded preceding window specification in a Spark DataFrame?🟡 Medium · Conceptual · Asked 1×How do you create a DataFrame with a column named 'current_amount'?🟢 Easy · Coding · Asked 1×

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