Python yield from完全指南 - 委托生成器与嵌套生成器

# 基础用法：等价替换
def old_way(iterable):
    """不使用yield from的方式"""
    for item in iterable:
        yield item

def new_way(iterable):
    """使用yield from的方式"""
    yield from iterable

# 两种写法完全等价
print(list(old_way([1, 2, 3])))   # [1, 2, 3]
print(list(new_way([1, 2, 3])))   # [1, 2, 3]

# 子生成器
def sub_generator():
    yield "子生成器: A"
    yield "子生成器: B"
    return "子生成器返回值"

# 委托生成器
def delegating_generator():
    yield "委托: 开始"
    result = yield from sub_generator()  # 委托给子生成器
    yield f"委托: 子生成器返回了 {result}"
    yield "委托: 结束"

# 使用
gen = delegating_generator()
for item in gen:
    print(item)
# 输出:
# 委托: 开始
# 子生成器: A
# 子生成器: B
# 委托: 子生成器返回了 子生成器返回值
# 委托: 结束

def flatten(nested):
    """递归展平任意深度的嵌套列表"""
    for item in nested:
        if isinstance(item, (list, tuple)):
            yield from flatten(item)  # 递归委托
        else:
            yield item

# 测试
data = [1, [2, [3, 4], 5], [6, 7]]
print(list(flatten(data)))
# [1, 2, 3, 4, 5, 6, 7]

data2 = [["a", "b"], ["c", ["d", "e"]], "f"]
print(list(flatten(data2)))
# ['a', 'b', 'c', 'd', 'e', 'f']

def even_numbers():
    for n in range(0, 10, 2):
        yield n

def odd_numbers():
    for n in range(1, 10, 2):
        yield n

def combined():
    yield "偶数:"
    yield from even_numbers()
    yield "奇数:"
    yield from odd_numbers()

print(list(combined()))
# ['偶数:', 0, 2, 4, 6, 8, '奇数:', 1, 3, 5, 7, 9]

def read_data():
    """模拟读取数据"""
    yield from [1, 2, 3, 4, 5]

def square(data):
    """对每个元素求平方"""
    for item in data:
        yield item ** 2

def filter_positive(data):
    """过滤负数"""
    for item in data:
        if item > 0:
            yield item

def process_pipeline():
    """组合管道：读取 -> 平方 -> 过滤"""
    yield from filter_positive(square(read_data()))

print(list(process_pipeline()))
# [1, 4, 9, 16, 25]