Many ML coding rounds include data manipulation tasks.
Common operations:
- Groupby aggregations
- Joins and merges
- Pivot tables
- Window functions (rolling, shift)
- Handling missing values
Example task: "Compute -day rolling average of user engagement, grouped by user type."
df.groupby('user_type')['engagement']
.rolling(7).mean().reset_index()
Interview tip: Practice data wrangling tasks. Know groupby, merge, and window functions cold.