Python 迭代器和生成器概念及场景分析

my_list = [1, 2, 3]
for x in my_list: print(x)  # 输出 1,2,3
for x in my_list: print(x)  # 再次输出 1,2,3

iterator = iter(my_list)
for x in iterator: print(x)  # 输出 1,2,3
for x in iterator: print(x)  # 无输出（迭代器已耗尽）

class CountUpTo:
    def __init__(self, max_num):
        self.max_num = max_num
        self.current = 0
    def __iter__(self):
        return self  # 返回迭代器本身
    def __next__(self):
        if self.current < self.max_num:
            self.current += 1
            return self.current
        else:
            raise StopIteration  # 终止迭代
# 使用自定义迭代器
counter = CountUpTo(3)
for num in counter:
    print(num)  # 输出 1, 2, 3

def count_up_to(max_num):
    current = 0
    while current < max_num:
        current += 1
        yield current
# 生成器返回的也是迭代器
for num in count_up_to(3):
    print(num)  # 输出 1, 2, 3

# 直接遍历列表
my_list = [1, 2, 3, 4, 5]
for x in my_list:
    print(x)

# 等价的手动迭代器操作
iterator = iter(my_list)  # 自动调用 __iter__() 获取迭代器
while True:
    try:
        x = next(iterator)  # 自动调用 __next__()
        print(x)
    except StopIteration:
        break  # 自动处理终止

def simple_generator():
    yield 1
    yield 2
    yield 3
gen = simple_generator()
print(next(gen))  # 输出 1
print(next(gen))  # 输出 2
print(next(gen))  # 输出 3
# 继续调用 next(gen) 会抛出 StopIteration 异常

def count_up_to(n):
    i = 0
    while i < n:
        yield i
        i += 1
for num in count_up_to(5):
    print(num)  # 输出 0, 1, 2, 3, 4

def generator_with_send():
	value = yield "Ready to receive"
	yield f"Received: {value}"
gen = generator_with_send()
print(next(gen))         # 输出 "Ready to receive"
print(gen.send("Hello")) # 输出 "Received: Hello"

def sub_generator():
	yield "A"
	yield "B"
def main_generator():
	yield from sub_generator()
	yield "C"
for item in main_generator():
	print(item)  # 输出 A, B, C

def generator_with_exception(value):
	try:
		yield 10 / value
	except ZeroDivisionError as e:
		yield "Caught ValueError"
gen = generator_with_exception(2)
print(next(gen))
gen = generator_with_exception(0)
print(next(gen))

def read_large_file(file_path):
    with open(file_path, "r") as file:
        for line in file:
            yield line.strip()  # 逐行生成，避免一次性加载到内存
for line in read_large_file("data.txt"):
    process(line)

def fibonacci():
    a, b = 0, 1
    while True:
        yield a
        a, b = b, a + b
fib = fibonacci()
print([next(fib) for _ in range(10)])  # 前10个斐波那契数

def coroutine():
    while True:
        task = yield
        print(f"Processing: {task}")
worker = coroutine()
next(worker)       # 启动协程
worker.send("Task1")  # 输出 "Processing: Task1"
worker.send("Task2")  # 输出 "Processing: Task2"