Find the quiet students in all exams

# Table: Student
# 
# +---------------------+---------+
# | Column Name         | Type    |
# +---------------------+---------+
# | student_id          | int     |
# | student_name        | varchar |
# +---------------------+---------+
# student_id is the primary key (column with unique values) for this table.
# student_name is the name of the student.
# 
#  
# 
# Table: Exam
# 
# +---------------+---------+
# | Column Name   | Type    |
# +---------------+---------+
# | exam_id       | int     |
# | student_id    | int     |
# | score         | int     |
# +---------------+---------+
# (exam_id, student_id) is the primary key (combination of columns with unique values) for this table.
# Each row of this table indicates that the student with student_id had a score points in the exam with id exam_id.
# 
#  
# 
# A quiet student is the one who took at least one exam and did not score the highest or the lowest score.
# 
# Write a solution to report the students (student_id, student_name) being quiet in all exams. Do not return the student who has never taken any exam.
# 
# Return the result table ordered by student_id.
# 
# The result format is in the following example.
#
# Example 1:
# Input:
# Student table:
# +-------------+---------------+
# | student_id  | student_name  |
# +-------------+---------------+
# | 1           | Daniel        |
# | 2           | Jade          |
# | 3           | Stella        |
# | 4           | Jonathan      |
# | 5           | Will          |
# +-------------+---------------+
# Exam table:
# +------------+--------------+-----------+
# | exam_id    | student_id   | score     |
# +------------+--------------+-----------+
# | 10         |     1        |    70     |
# | 10         |     2        |    80     |
# | 10         |     3        |    90     |
# | 20         |     1        |    80     |
# | 30         |     1        |    70     |
# | 30         |     3        |    80     |
# | 30         |     4        |    90     |
# | 40         |     1        |    60     |
# | 40         |     2        |    70     |
# | 40         |     4        |    80     |
# +------------+--------------+-----------+
# Output:
# +-------------+---------------+
# | student_id  | student_name  |
# +-------------+---------------+
# | 2           | Jade          |
# +-------------+---------------+
# Explanation:
# For exam 1: Student 1 and 3 hold the lowest and high scores respectively.
# For exam 2: Student 1 hold both highest and lowest score.
# For exam 3 and 4: Student 1 and 4 hold the lowest and high scores respectively.
# Student 2 and 5 have never got the highest or lowest in any of the exams.
# Since student 5 is not taking any exam, he is excluded from the result.
# So, we only return the information of Student 2.

import pandas as pd

def find_quiet_students(student: pd.DataFrame, exam: pd.DataFrame) -> pd.DataFrame:
  if exam.empty:
    return pd.DataFrame(columns=['student_id', 'student_name'])
  exam = exam.merge(
    exam.groupby('exam_id')['score'].agg(['min', 'max']),
    on='exam_id'
  )
  loud = exam[(exam['score'] == exam['min']) | (exam['score'] == exam['max'])]['student_id'].unique()
  took_exam = exam['student_id'].unique()
  quiet_ids = set(took_exam) - set(loud)
  result = student[student['student_id'].isin(quiet_ids)][['student_id', 'student_name']]
  return result.sort_values('student_id')