7.3 value_counts vs GroupBy
df["city"].value_counts()
df.groupby("city").size() # similar counts
df.groupby("status")["amount"].sum()
Worked example. Ruhi Bagale compares Diwali vs None GMV for Pune before sending a note to Ravindra Bagale (city manager).
Practice task
Add a platform column (Blinkit / Amazon Now). Group by platform and city to get GMV and order counts. Sort by GMV descending.
Thodkyaat sangaycha tar (quick recap)
- groupby = split–apply–combine
- Named aggregations give clean report columns
- Use nunique on order_id when grain is line-level
Samajla ka? Aata pudhe jaauya combining data — concat and merge.