Python-time和datetime模块

一、time模块

1、表示时间的三种方式

>>> import time

>>> time.time()  #当前时间戳
1509525556.8485825

>>> time.localtime()  #用struct_time结构保存当前时间
time.struct_time(tm_year=2017, tm_mon=11, tm_mday=1, tm_hour=16, tm_min=39, tm_s
ec=24, tm_wday=2, tm_yday=305, tm_isdst=0)

>>> time.strftime('%Y-%m-%d %H:%M:%S', time.localtime()) #用字符串形式格式化时间
'2017-11-01 16:39:38'

2、三种格式之间的相互转化

>>> time.gmtime(time.time()) #时间戳转化为struct_time
time.struct_time(tm_year=2017, tm_mon=11, tm_mday=1, tm_hour=8, tm_min=53, tm_se
c=51, tm_wday=2, tm_yday=305, tm_isdst=0)

>>> time.mktime(time.localtime()) #struct_time转化为时间戳
1509526449.0

>>> time.strftime('%Y-%m-%d %H:%M:%S', time.localtime()) #struct_time转化为字符串
'2017-11-01 16:54:27'

>>> time.strptime('2017-11-01', '%Y-%m-%d') #字符串转化为struct_time
time.struct_time(tm_year=2017, tm_mon=11, tm_mday=1, tm_hour=0, tm_min=0, tm_sec
=0, tm_wday=2, tm_yday=305, tm_isdst=-1)

3、time.sleep()表示间隔多少秒再继续

>>> while True:
        print('hello')
        time.sleep(1)  #表示每隔1秒打印一次‘hello’

二、datetime模块

import datatime

print(datetime.datetime.now())  #获取当前日期和时间
print(datetime.datetime.now()+datetime.timedelta(3))  #3天后的时间
print(datetime.datetime.now()+datetime.timedelta(-3)) #3天前的时间