程序也出错？还无法矫正！

各位仁人志士们，真心不难，但困扰我许久了，求解答~111
#DayDayUp Q4.py
def dayUP(df):
dayup = 1
for i in range(365):
if i & 7 in [6,0]:
dayup = dayup *(1 - 0.01)
else:
dayup = dayup *(1 + df)
return dayup
dayfactor =0.01
while dayUP(dayfactor) < 37.78:
dayfactor += 0.001
print("工作日的努力参数：{:.3f}".format(dayfactor))
结果行
===== RESTART: F:\Jenkin Li\Draft\Python-try\study\3.4DD4条件循环判断 - 副本.py =====
工作日的努力参数：0.017
实际应该是0.019