python 时间转换

import datetime

# 将字符串转换成时间

start_time = '201808201000'
now_datetime = datetime.datetime.strptime(start_time, '%Y%m%d%H%M')
其中"%Y%m%d %H%M%S"为time字符串的时间格式 Y为年，m为月，d为天，H为小时，M为分钟，S为秒，执行转化结果如下
2018-08-20 10:00:00

如果我们要加的时间是天，当前时间加上datetime.timedelta(days=1)。datetime的timedelta方法实现
low_datetime = now_datetime + datetime.timedelta(days=1)

如果要加的时间是小时则如下，当前时间加上datetime.timedelta(hour

s=1)

low_datetime = now_datetime + datetime.timedelta(hours=1)

如果要加的时间是分钟则如下，当前时间加上datetime.timedelta(minutes=1)

low_datetime = now_datetime + datetime.timedelta(minutes=1)
print(low_datetime)

如果加的时间是秒的话，如下当前时间加上datetime.timedelta(seconds=1)

low_datetime = now_datetime + datetime.timedelta(seconds=1)
print(low_datetime)

时间转换成字符串

low_datetime = now_datetime - datetime.timedelta(minutes=2)
low_datetime = low_datetime.strftime('%Y%m%d%H%M')
print(low_datetime)

import datetime
from datetime import timedelta
now = datetime.datetime.now()
#今天
today = now
#昨天
yesterday = now - timedelta(days=1)
#明天
tomorrow = now + timedelta(days=1)

#当前季度 
now_quarter = now.month / 3 if now.month % 3 == 0 else now.month / 3 + 1
#本周第一天和最后一天
this_week_start = now - timedelta(days=now.weekday())
this_week_end = now + timedelta(days=6-now.weekday())
#上周第一天和最后一天
last_week_start = now - timedelta(days=now.weekday()+7)
last_week_end = now - timedelta(days=now.weekday()+1)
#本月第一天和最后一天
this_month_start = datetime.datetime(now.year, now.month, 1)
this_month_end = datetime.datetime(now.year, now.month + 1, 1) - timedelta(days=1)
#上月第一天和最后一天
last_month_end = this_month_start - timedelta(days=1)
last_month_start = datetime.datetime(last_month_end.year, last_month_end.month, 1)
#本季第一天和最后一天
month = (now.month - 1) - (now.month - 1) % 3 + 1
this_quarter_start = datetime.datetime(now.year, month, 1)
this_quarter_end = datetime.datetime(now.year, month + 3, 1) - timedelta(days=1)
#上季第一天和最后一天
last_quarter_end = this_quarter_start - timedelta(days=1)
last_quarter_start = datetime.datetime(last_quarter_end.year, last_quarter_end.month - 2, 1)
 #本年第一天和最后一天
this_year_start = datetime.datetime(now.year, 1, 1)
this_year_end = datetime.datetime(now.year + 1, 1, 1) - timedelta(days=1)

#去年第一天和最后一天
last_year_end = this_year_start - timedelta(days=1)
last_year_start = datetime.datetime(last_year_end.year, 1, 1)