python中如何覆盖父类的方法

import threading
import time
def catch_fish():
Pass
def one_thread():   
 start_time = time.time()    
for i in range(1, 1001):       
 catch_fish()    
end_time = time.time()    
print("单线程测试 耗时 === %s" % str(end_time - start_time))
def muti_thread():   
 start_time = time.time()   
 for i in range(1, 1001):        
threading.Thread(target=catch_fish()).start()    
end_time = time.time()    
print("多线程测试 耗时 === %s" % str(end_time - start_time))
if __name__ == '__main__':    
# 单线程    
threading.Thread(one_thread()).start()    
# 多线程    
muti_thread()