线程（调用的两种方法、全局变量共享、线程数量）

# -*- coding:utf-8 -*-
# Author:Sure Feng


import threading
import time


num = 0


def sing():
    # 线程间共享全局变量，可能导致数据混乱
    global num
    for i in range(5000):
        num += 1
        print("--第【%d】次sing----" % num)
        # time.sleep(0.1)


class Dance(threading.Thread):
    def run(self):
        global num
        for i in range(5000):
            num += 1
            print("---第【%d】次dance---" % num)
            # time.sleep(0.1)


def main():
    # 调用线程的第一种方法
    t1 = threading.Thread(target=sing)
    # 调用线程的第二种方法
    t2 = Dance()
    t1.start()
    t2.start()

    while True:
        # 查看当前线程数量
        threading_num = len(threading._enumerate())
        print("当前的线程数量为%d" % threading_num)
        if threading_num <= 1:
            break

        # time.sleep(0.3)

if __name__ == "__main__":
    main()