def time_for_next_update(last_time, period='D', hour=9):
"""计算下次更新时间
说明：
'D'：移动到下一天
'W'：移动到下周一
'M'：移动到下月第一天
'Q'：下一季度的第一天
将小时调整到指定的hour
"""
if pd.isnull(last_time):
return MARKET_START
period = period.upper()
if period == 'D':
d = BDay(normalize=True)
return d.apply(last_time).replace(hour=hour)
elif period == 'W':
w = Week(normalize=True, weekday=0)
return w.apply(last_time).replace(hour=hour)
elif period == 'M':
m = MonthBegin(normalize=True)
return m.apply(last_time).replace(hour=hour)
elif period == 'Q':
q = QuarterBegin(normalize=True)
return q.apply(last_time).replace(hour=hour)
else:
raise TypeError('不能识别的周期类型，仅接受{}'.format(('D', 'W', 'M', 'Q')))
