👀 Views: 1457 💬 Answers: 1 📅 Created: 2025-06-04

python sorting comparator Python

I'm performance testing and I'm working on a project and hit a roadblock. I'm trying to sort a list of dictionaries in Python using a custom comparator that sorts primarily by one key and secondarily by another. However, I'm getting unexpected results. I have a list of dictionaries representing students, where each dictionary has 'name', 'age', and 'grade'. I want to sort by 'age' first and then by 'grade'. Here’s the code I have so far: ```python students = [ {'name': 'Alice', 'age': 22, 'grade': 88}, {'name': 'Bob', 'age': 22, 'grade': 85}, {'name': 'Charlie', 'age': 21, 'grade': 90}, {'name': 'David', 'age': 23, 'grade': 75} ] # Custom sorting function def custom_sort(student): return (student['age'], student['grade']) # Sorting the list students_sorted = sorted(students, key=custom_sort) print(students_sorted) ``` When I run this code, I expect the output to list the students sorted by age first and then by grade, but the sorted order seems off. Specifically, Alice and Bob have the same age, but the order does not retain the original insertion order when they have the same age. I tried using a tuple to sort, but it seems like the sort is not stable. I read that Python’s sort is stable, so I’m a bit puzzled. Could someone explain why this is happening or suggest a solution? I’m using Python 3.9.6. Any help would be greatly appreciated! For context: I'm using Python on Linux. Has anyone else encountered this? This is part of a larger CLI tool I'm building. For reference, this is a production web app. What's the correct way to implement this?