一文带你深入了解Python中的多进程编程

import multiprocessing
import os
import time
 
def worker():
    print(f"Worker process id: {os.getpid()}")
    time.sleep(2)
    print("Worker process finished")
 
if __name__ == "__main__":
    print(f"Main process id: {os.getpid()}")
    p = multiprocessing.Process(target=worker)
    p.start()
    p.join()  # 等待进程结束
    print("Main process finished")

import multiprocessing
import time
 
def worker(q):
    time.sleep(2)
    q.put("Hello from worker")
 
if __name__ == "__main__":
    q = multiprocessing.Queue()
    p = multiprocessing.Process(target=worker, args=(q,))
    p.start()
    result = q.get()  # 获取进程发送的数据
    print(result)
    p.join()

import multiprocessing
import time
 
def worker(conn):
    time.sleep(2)
    conn.send("Hello from worker")
    conn.close()
 
if __name__ == "__main__":
    parent_conn, child_conn = multiprocessing.Pipe()
    p = multiprocessing.Process(target=worker, args=(child_conn,))
    p.start()
    result = parent_conn.recv()  # 接收进程发送的数据
    print(result)
    p.join()

import multiprocessing
import os
import time
 
def worker(x):
    print(f"Worker process id: {os.getpid()}, argument: {x}")
    time.sleep(2)
    return x * x
 
if __name__ == "__main__":
    with multiprocessing.Pool(processes=4) as pool:  # 创建一个包含4个进程的进程池
        results = pool.map(worker, range(10))  # 将任务分配给进程池中的进程
    print(results)

import multiprocessing
import time
 
def worker(lock, x):
    with lock:  # 获取锁
        print(f"Worker {x} is working")
        time.sleep(2)
        print(f"Worker {x} finished")
 
if __name__ == "__main__":
    lock = multiprocessing.Lock()
    processes = []
    for i in range(5):
        p = multiprocessing.Process(target=worker, args=(lock, i))
        processes.append(p)
        p.start()
 
    for p in processes:
        p.join()

import multiprocessing
import os
from PIL import Image
 
def process_image(file_path, output_dir):
    img = Image.open(file_path)
    img.thumbnail((128, 128))  # 缩放图像
    img_name = os.path.basename(file_path)
    img.save(os.path.join(output_dir, img_name))
 
def main(input_dir, output_dir, num_processes):
    if not os.path.exists(output_dir):
        os.makedirs(output_dir)
 
    image_files = [os.path.join(input_dir, f) for f in os.listdir(input_dir) if f.endswith(('png', 'jpg', 'jpeg'))]
 
    with multiprocessing.Pool(processes=num_processes) as pool:
        pool.starmap(process_image, [(img_file, output_dir) for img_file in image_files])
 
if __name__ == "__main__":
    input_dir = "path/to/input/images"
    output_dir = "path/to/output/images"
    num_processes = 4
    main(input_dir, output_dir, num_processes)