# 创建列表迭代器
my_list = [1, 2, 3, 4, 5]
my_iterator = iter(my_list)

# 获取迭代器的下一个元素
print(next(my_iterator))  # 1
print(next(my_iterator))  # 2
print(next(my_iterator))  # 3

# 创建列表迭代器
my_list = [1, 2, 3]
my_iterator = iter(my_list)

# 获取迭代器的下一个元素，设置默认值为 None
print(next(my_iterator, None))  # 1
print(next(my_iterator, None))  # 2
print(next(my_iterator, None))  # 3
print(next(my_iterator, None))  # None

# 打开文件

lines = ['line 1\n', 'line 2\n', 'line 3\n']
with open('example.txt', 'w') as f:
    f.writelines(lines)

file_path = "example.txt"
with open(file_path) as f:
    # 创建文件迭代器
    file_iterator = iter(f)
    try:
        while True:
            # 逐行读取文件内容
            line = next(file_iterator)
            print(line, end="")
    except StopIteration:
        pass


class MyIterator:
    def __init__(self, start, end):
        self.current = start
        self.end = end

    def __iter__(self):
        return self

    def __next__(self):
        if self.current >= self.end:
            raise StopIteration
        else:
            self.current += 1
            return self.current - 1


# 使用自定义迭代器
my_iterator = MyIterator(1, 5)
print(next(my_iterator))  # 1
print(next(my_iterator))  # 2
print(next(my_iterator))  # 3

# 创建列表迭代器
my_list = [1, 2, 3, 4, 5]
my_iterator = iter(my_list)

# 跳过前两个元素
next(my_iterator)
next(my_iterator)

# 获取迭代器的下一个元素
print(next(my_iterator))  # 3


def infinite_sequence():
    num = 0
    while True:
        yield num
        num += 1


# 创建生成器
gen = infinite_sequence()

# 获取生成器的前几个元素
for _ in range(5):
    print(next(gen))

# 创建嵌套列表
nested_list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

# 创建迭代器
iterator = iter(nested_list)

# 获取迭代器的下一个元素
print(next(iterator))  # [1, 2, 3]
print(next(iterator))  # [4, 5, 6]
print(next(iterator))  # [7, 8, 9]