python计算时间差

from datetime import datetime
import time

a = datetime.now() # 获得当前时间
time.sleep(2)       # sleep 2s
b = datetime.now()  # 获取当前时间
res = (b-a).seconds  # 时间差，以秒显示
print(res )


start = time.time()

time.sleep(3)

end  = time.time()

res = f'{end - start :.2f}'