# 常见的可迭代对象
my_list = [1, 2, 3]  # 列表
my_tuple = (1, 2, 3)  # 元组
my_string = "hello"  # 字符串
my_dict = {"a": 1, "b": 2}  # 字典
my_set = {1, 2, 3}  # 集合

# 使用for循环遍历
for item in my_list:
    print(item)

# 使用iter()函数
iter_obj = iter(my_list)  # 等同于  my_list.__iter__()
print(next(iter_obj))  # 等同于 iter_obj.__next__()
print(next(iter_obj))
print(next(iter_obj))　

# 自定义迭代器
class MyIterator:
    def __init__(self, max_value):
        self.max_value = max_value
        self.current = 0
    
    def __iter__(self):
        return self
    
    def __next__(self):
        if self.current < self.max_value:
            self.current += 1
            return self.current - 1
        else:
            raise StopIteration

# 使用自定义迭代器
my_iter = MyIterator(5)
print(next(my_iter))  # 0
print(next(my_iter))  # 1
print(next(my_iter))  # 2

# 或者用for循环
for num in MyIterator(3):
    print(num)  # 0, 1, 2
	



示例1：自定义数字范围迭代器	
	class NumberRange:
    """自定义数字范围迭代器"""
    def __init__(self, start, end, step=1):
        self.current = start
        self.end = end
        self.step = step
    
    def __iter__(self):
        return self
    
    def __next__(self):
        if self.current >= self.end:
            raise StopIteration
        current_value = self.current
        self.current += self.step
        return current_value

# 使用迭代器
print("数字范围迭代器:")
numbers = NumberRange(1, 6)  # 1到5
for num in numbers:
    print(num, end=" ")  # 输出: 1 2 3 4 5
	



#简化版
def my_range(start, stop, step=1):
   while start < stop:
       yield start
       start += step

for i in my_range(1,5,2):  # 1 3
    print(i)

def countdown(n):
    """生成器函数示例"""
    print("开始倒计时")
    while n > 0:
        yield n
        n -= 1
    print("发射!")

# 使用生成器
cd = countdown(5)
print(cd)  #实际指向了内存地址，并不存储真实数据 <generator object countdown at 0x000001CF42EEE2C0>
print(next(cd))  # 5
print(next(cd))  # 4
print(next(cd))  # 3

# 或者用for循环
for num in countdown(3):
    print(num)  # 3, 2, 1
	

# 类似于列表推导式，但使用圆括号
squares = (x*x for x in range(5)) # 类别生成式格式为 [x*x for x in range(5)] ，注意没有元组生成式，因为()给了生成器

print(next(squares))  # 0
print(next(squares))  # 1
print(next(squares))  # 4

# 或者转换为列表
result = list(squares)
print(result)  # [9, 16]	

场景1：处理大型数据集（内存优化）
python
def read_large_file(file_path):
    """逐行读取大文件，避免内存溢出"""
    with open(file_path, 'r', encoding='utf-8') as file:
        for line in file:
            yield line.strip()

# 使用示例
for line in read_large_file('large_data.txt'):
    # 处理每一行数据
    if 'error' in line:
        print(line)
		
		
		
场景2：简单的计数器生成器
python
def simple_counter(limit):
    """简单的计数器生成器"""
    count = 1
    while count <= limit:
        yield count
        count += 1

# 使用生成器
print("\n计数器生成器:")
counter = simple_counter(5)
for num in counter:
    print(num, end=" ")  # 输出: 1 2 3 4 5