（4）学生管理：包括添加学生信息，删除学生信息，修改学生信息，查询学生信息（按学号查询学生信息、按姓名查询学生信息、查询某个班级的学生信息、查询某个学院的学生信息）；学生属于某个班级。帮我写代码

好的，以下是一个简单的学生管理系统的代码示例，其中包含添加、删除、修改和查询学生信息的功能，以及学生属于班级的关联：

class Student:
    def __init__(self, id, name, gender, age, class_id):
        self.id = id
        self.name = name
        self.gender = gender
        self.age = age
        self.class_id = class_id

class Class:
    def __init__(self, id, name):
        self.id = id
        self.name = name
        self.students = []

class College:
    def __init__(self, id, name):
        self.id = id
        self.name = name
        self.classes = []

class StudentManager:
    def __init__(self):
        self.colleges = []

    def add_student(self, id, name, gender, age, class_id):
        # find the class that the student belongs to
        class_obj = None
        for college in self.colleges:
            for class_obj in college.classes:
                if class_obj.id == class_id:
                    break
            if class_obj:
                break

        if not class_obj:
            print(f"Error: class {class_id} not found")
            return

        # add the student to the class
        student = Student(id, name, gender, age, class_id)
        class_obj.students.append(student)

    def delete_student(self, id):
        # find the student to delete
        for college in self.colleges:
            for class_obj in college.classes:
                for student in class_obj.students:
                    if student.id == id:
                        class_obj.students.remove(student)
                        return

        print(f"Error: student {id} not found")

    def update_student(self, id, name, gender, age, class_id):
        # find the student to update
        for college in self.colleges:
            for class_obj in college.classes:
                for student in class_obj.students:
                    if student.id == id:
                        student.name = name
                        student.gender = gender
                        student.age = age
                        student.class_id = class_id
                        return

        print(f"Error: student {id} not found")

    def search_student_by_id(self, id):
        # find the student by id
        for college in self.colleges:
            for class_obj in college.classes:
                for student in class_obj.students:
                    if student.id == id:
                        return student

        print(f"Error: student {id} not found")
        return None

    def search_student_by_name(self, name):
        # find the student by name
        result = []
        for college in self.colleges:
            for class_obj in college.classes:
                for student in class_obj.students:
                    if student.name == name:
                        result.append(student)

        if len(result) == 0:
            print(f"Error: student {name} not found")

        return result

    def search_student_by_class(self, class_id):
        # find the students in a class
        result = []
        for college in self.colleges:
            for class_obj in college.classes:
                if class_obj.id == class_id:
                    result.extend(class_obj.students)

        if len(result) == 0:
            print(f"Error: class {class_id} not found")

        return result

    def search_student_by_college(self, college_id):
        # find the students in a college
        result = []
        for college in self.colleges:
            if college.id == college_id:
                for class_obj in college.classes:
                    result.extend(class_obj.students)

        if len(result) == 0:
            print(f"Error: college {college_id} not found")

        return result

    def add_class(self, id, name, college_id):
        # find the college to add the class to
        college = None
        for c in self.colleges:
            if c.id == college_id:
                college = c
                break

        if not college:
            print(f"Error: college {college_id} not found")
            return

        # add the class to the college
        class_obj = Class(id, name)
        college.classes.append(class_obj)

    def delete_class(self, id):
        # find the class to delete
        for college in self.colleges:
            for class_obj in college.classes:
                if class_obj.id == id:
                    college.classes.remove(class_obj)
                    return

        print(f"Error: class {id} not found")

    def update_class(self, id, name):
        # find the class to update
        for college in self.colleges:
            for class_obj in college.classes:
                if class_obj.id == id:
                    class_obj.name = name
                    return

        print(f"Error: class {id} not found")

    def search_class_by_id(self, id):
        # find the class by id
        for college in self.colleges:
            for class_obj in college.classes:
                if class_obj.id == id:
                    return class_obj

        print(f"Error: class {id} not found")
        return None

    def search_class_by_name(self, name):
        # find the class by name
        result = []
        for college in self.colleges:
            for class_obj in college.classes:
                if class_obj.name == name:
                    result.append(class_obj)

        if len(result) == 0:
            print(f"Error: class {name} not found")

        return result

    def add_college(self, id, name):
        # add a new college
        college = College(id, name)
        self.colleges.append(college)

    def delete_college(self, id):
        # find the college to delete
        for college in self.colleges:
            if college.id == id:
                self.colleges.remove(college)
                return

        print(f"Error: college {id} not found")

    def update_college(self, id, name):
        # find the college to update
        for college in self.colleges:
            if college.id == id:
                college.name = name
                return

        print(f"Error: college {id} not found")

    def search_college_by_id(self, id):
        # find the college by id
        for college in self.colleges:
            if college.id == id:
                return college

        print(f"Error: college {id} not found")
        return None

    def search_college_by_name(self, name):
        # find the college by name
        result = []
        for college in self.colleges:
            if college.name == name:
                result.append(college)

        if len(result) == 0:
            print(f"Error: college {name} not found")

        return result

使用示例：

manager = StudentManager()

# add some colleges
manager.add_college(1, "College of Engineering")
manager.add_college(2, "College of Science")

# add some classes
manager.add_class(101, "Class 1", 1)
manager.add_class(102, "Class 2", 1)
manager.add_class(201, "Class 3", 2)
manager.add_class(202, "Class 4", 2)

# add some students
manager.add_student(1, "Alice", "F", 20, 101)
manager.add_student(2, "Bob", "M", 21, 101)
manager.add_student(3, "Charlie", "M", 19, 102)
manager.add_student(4, "David", "M", 22, 201)
manager.add_student(5, "Eve", "F", 20, 201)

# update a student's information
manager.update_student(1, "Alicia", "F", 20, 102)

# search for a student by id
student = manager.search_student_by_id(1)
print(student.name)  # should print "Alicia"

# search for students by name
students = manager.search_student_by_name("Bob")
for student in students:
    print(student.id, student.name)  # should print "2 Bob"

# search for students in a class
students = manager.search_student_by_class(201)
for student in students:
    print(student.id, student.name)  # should print "4 David" and "5 Eve"

# search for students in a college
students = manager.search_student_by_college(1)
for student in students:
    print(student.id, student.name)  # should print "1 Alicia", "2 Bob", and "3 Charlie"

# delete a student
manager.delete_student(3)

# add a new college
manager.add_college(3, "College of Arts")

# delete a class
manager.delete_class(202)

# update a class's name
manager.update_class(201, "New Class Name")

# search for a class by id
class_obj = manager.search_class_by_id(101)
print(class_obj.name)  # should print "Class 1"

# search for classes by name
classes = manager.search_class_by_name("Class 2")
for class_obj in classes:
    print(class_obj.id, class_obj.name)  # should print "102 Class 2"

# search for a college by id
college = manager.search_college_by_id(2)
print(college.name)  # should print "College of Science"

# search for colleges by name
colleges = manager.search_college_by_name("College of Engineering")
for college in colleges:
    print(college.id, college.name)  # should print "1 College of Engineering"