Multi-Key Sorting with Lambda Functions in Python

Question

Given a list of client dicts with `name`, `tier` (1 to 3, where 1 is highest), and `revenue`, sort the clients primarily by `tier` ascending, and secondarily by `revenue` descending.

Accepted Answer

Optimal Solution:
def sort_clients(clients: list[dict]) -> list[dict]:
    # Tuple key: (tier ASC, -revenue DESC)
    return sorted(
        clients, 
        key=lambda c: (c['tier'], -c['revenue'])
    )

Technical Explanation:
Python's `sorted()` accepts a key function returning a tuple. Inverting numerical values (`-c['revenue']`) provides descending sort order alongside ascending tier.

name	tier	revenue
Gamma Inc	1	95000
Acme Corp	1	50000
Beta LLC	2	80000