1. 自定义多线程程序：

import concurrent.futures
import threading

class CustomThreadPool:
    def __init__(self, max_workers):
        self.max_workers = max_workers
        self.pool = concurrent.futures.ThreadPoolExecutor(max_workers)
        self.running_num = 0
        self.semaphore = threading.Semaphore(max_workers)
    
    def submit(self, fn, *args, **kwargs):
        self.semaphore.acquire()  # 获取信号量（如果已满则阻塞）
        self.running_num += 1
        
        future = self.pool.submit(fn, *args, **kwargs)
        future.add_done_callback(self._callback)
        return future
    
    def _callback(self, future):
        self.running_num -= 1
        self.semaphore.release()  # 释放信号量，允许新任务提交
    
    def shutdown(self):
        self.pool.shutdown()

以上程序实现：使用这个自定义线程池时，当并发任务数达到上限后，新提交的任务会被阻塞，直到有任务完成。

使用程序：

import time
import random
from custom_threadpool import CustomThreadPool  # 假设上面的类保存在 custom_threadpool.py 中

# 模拟下载图片的函数（实际应用中可替换为 requests.get 等真实下载逻辑）
def download_image(url):
    # 模拟网络请求延迟
    delay = random.uniform(0.5, 2.0)
    time.sleep(delay)
    
    # 模拟下载结果
    size = random.randint(100, 1000)
    print(f"下载完成: {url} (大小: {size}KB, 耗时: {delay:.2f}s)")
    return {"url": url, "size": size, "status": "success"}

# 主程序
def main():
    # 创建一个最大并发数为3的线程池
    with CustomThreadPool(max_workers=3) as pool:
        # 模拟10个图片下载任务
        image_urls = [f"https://example.com/image_{i}.jpg" for i in range(1, 11)]
        
        # 提交所有下载任务
        futures = []
        for url in image_urls:
            future = pool.submit(download_image, url)
            futures.append(future)
        
        # 获取所有任务的结果（按完成顺序输出）
        for future in concurrent.futures.as_completed(futures):
            try:
                result = future.result()
                print(f"处理结果: {result['url']} ({result['size']}KB)")
            except Exception as e:
                print(f"下载失败: {e}")

if __name__ == "__main__":
    start_time = time.time()
    main()
    print(f"总耗时: {time.time() - start_time:.2f}秒")

2.* ** 参数：

def example(a, b, *args, **kwargs):
    print(f"固定参数：a={a}, b={b}")
    print(f"位置参数：{args}")
    print(f"关键字参数：{kwargs}")

example(1, 2, 3, 4, x=5, y=6)
# 输出：
# 固定参数：a=1, b=2
# 位置参数：(3, 4)
# 关键字参数：{'x': 5, 'y': 6}