单线程：

import threading
import time


def sing():
    while True:
        print("我在唱歌")
        time.sleep(1)
def dance():
    while True:
        print("我在跳舞")
        time.sleep(1)
if __name__=="__main__":
    sing()
    dance()

多线程：

import threading
import time


def sing():
    while True:
        print("我在唱歌")
        time.sleep(1)
def dance():
    while True:
        print("我在跳舞")
        time.sleep(1)
if __name__=="__main__":
    singThread = threading.Thread(target=sing)
    danceThread = threading.Thread(target=dance)
    singThread.start()
    danceThread.start()

import threading
import time


def sing(msg):
    while True:
        print(msg)
        time.sleep(1)
def dance(msg):
    while True:
        print(msg)
        time.sleep(1)
if __name__=="__main__":
    singThread = threading.Thread(target=sing,args=("我在唱歌",))
    danceThread = threading.Thread(target=dance,kwargs={"msg":"我在跳舞"})
    singThread.start()
    danceThread.start()