Python迭代器和生成器之迭代器协议详解

class MyIterator:
    def __init__(self, data):
        self.data = data
        self.index = 0

    def __iter__(self):
        return self

    def __next__(self):
        if self.index < len(self.data):
            result = self.data[self.index]
            self.index += 1
            return result
        else:
            raise StopIteration

# 使用自定义迭代器
my_iter = MyIterator([1, 2, 3, 4])
for item in my_iter:
    print(item)

class CountIterator:
    def __init__(self, start=0):
        self.current = start

    def __iter__(self):
        return self

    def __next__(self):
        self.current += 1
        return self.current - 1

# 使用自定义迭代器
counter = CountIterator()
for _ in range(10):
    print(next(counter))

class FibonacciIterator:
    def __init__(self):
        self.a, self.b = 0, 1

    def __iter__(self):
        return self

    def __next__(self):
        self.a, self.b = self.b, self.a + self.b
        return self.a

# 使用斐波那契数列迭代器
fib = FibonacciIterator()
for _ in range(10):
    print(next(fib))

class FileIterator:
    def __init__(self, filename):
        self.file = open(filename, 'r')

    def __iter__(self):
        return self

    def __next__(self):
        line = self.file.readline()
        if not line:
            self.file.close()
            raise StopIteration
        return line.strip()

# 使用文件迭代器
file_iter = FileIterator('example.txt')
for line in file_iter:
    print(line)

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

    def __str__(self):
        return f'ID: {self.id}, Name: {self.name}, Age: {self.age}'

class StudentIterator:
    def __init__(self, students):
        self.students = students
        self.index = 0

    def __iter__(self):
        return self

    def __next__(self):
        if self.index < len(self.students):
            student = self.students[self.index]
            self.index += 1
            return student
        else:
            raise StopIteration

from student import Student
from student_iterator import StudentIterator

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

    def add_student(self, id, name, age):
        student = Student(id, name, age)
        self.students.append(student)

    def remove_student(self, id):
        self.students = [s for s in self.students if s.id != id]

    def find_student(self, id):
        for student in self.students:
            if student.id == id:
                return student
        return None

    def __iter__(self):
        return StudentIterator(self.students)

# 测试学生管理系统
manager = StudentManager()
manager.add_student(1, 'Alice', 20)
manager.add_student(2, 'Bob', 22)
manager.add_student(3, 'Charlie', 21)

print('所有学生:')
for student in manager:
    print(student)

print('\n查找学生ID为2的学生:')
print(manager.find_student(2))

print('\n移除学生ID为1的学生:')
manager.remove_student(1)

print('\n所有学生:')
for student in manager:
    print(student)