import requests, time
from threading import Thread


class MyThread(Thread):
    def __init__(self, url):
        Thread.__init__(self)
        self.url = url

    def run(self):
        open_url(self.url)


def open_url(url):
    r = requests.get(url[:-1])
    print(r.status_code)
    print(url)
    # return url


if __name__ == '__main__':
    with open("E:/all_domain.txt",'r') as f:
        t_start = time.time()
        threads = []
        for url in f:
            t = MyThread(url)
            threads.append(t)
            t.start()
            print(len(threads))
        for i in threads:
            i.join()
        t_end = time.time()
        print('the thread way take %s s' % (t_end - t_start))

上面是我写的一个多进程。f文件里面大概有18万条数据，执行多线程的时候难道打开18万个线程吗？要怎么改写控制线程数量？譬如说先100个线程，100个线程结束后在开100个线程。
线程是在一个cpu核心里面运行，有办法做到多核心多线程吗？要如何改写呢？
谢谢！