谈谈python time datetime timestamp之间转换

python中的时间表示形式

---

1. string
   字符串形式表示时间：time.ctime()
2. datetime
   In [15]: datetime.datetime.now()
   Out[15]: datetime.datetime(2018, 11, 14, 16, 38, 16, 152438)
3. time
   In [14]: time.localtime()
   Out[14]: time.struct_time(tm_year=2018, tm_mon=11, tm_mday=14, tm_hour=16, tm_min=36, tm_sec=18, tm_wday=2, tm_yday=318, tm_isdst=0)
4. timestamp:
   自1970年1月1日(00:00:00 GMT)以来的秒数
   In [16]: time.time()
   Out[16]: 1542184899.844029

上述几种表现形式之间的转换

---

1. string ==================> datetime
   datetime.strpftime(format)

   datetime.strptime(str, format)
      In [17]: t_str="2018-11-14 16:50"
      
      In [18]: datetime.datetime.strptime(t_str, "%Y-%m-%d %H:%M")
      Out[18]: datetime.datetime(2018, 11, 14, 16, 50)
   

2. string ==================> time

   time.strptime(str, format)
       In [20]: time.strptime(t_str, "%Y-%m-%d %H:%M")
       Out[20]: time.struct_time(tm_year=2018, tm_mon=11, tm_mday=14, tm_hour=16, tm_min=50, tm_sec=0, tm_wday=2, tm_yday=318, tm_isdst=-1)
       ```
   

3. string ===================> timestamp
   一般不能直接转换，都是通过先转换为datetime或者time后在进一步做转换

4. datetime =================> string
   dt_obj.strftime(format)

       In [21]: t_datetime = datetime.datetime.now()
       
       In [25]: t_datetime.strftime("%Y-%m-%D %H:%M")
       Out[25]: '2018-11-11/14/18 17:00'
       In [26]: type(t_datetime.strftime("%Y-%m-%D %H:%M"))
       Out[26]: str
   

5. datetime =================> time
   dt_obj.timetuple()

      In [27]: t_datetime.timetuple()
      Out[27]: time.struct_time(tm_year=2018, tm_mon=11, tm_mday=14, tm_hour=17, tm_min=0, tm_sec=11, tm_wday=2, tm_yday=318, tm_isdst=-1)
   

6. datetime ================> timestamp
   python3中 新加了一个函数dt_obj.timestamp()，可以直接转换
   python2中 datetime ----timetuple()----->time_obj --------time.mktime(time_obj) ----->timestamp

7. time ===================> string
   time.strftime(fromat, time_obj)

       In [39]: time.strftime("%Y-%m-%d %H:%M", t_obj)
       Out[39]: '2018-11-14 17:21'
   

8. time ===================> datetime
   datetime.datetime(*t_obj[0:6])

       In [42]: datetime.datetime(*t_obj[0:6])
       Out[42]: datetime.datetime(2018, 11, 14, 17, 21, 39)
   

9. time ====================> timestamp
   time.mktime(t_obj)

    In [43]: time.mktime(t_obj)
    Out[43]: 1542187299.0

11. timestamp ================> datetime
    datetime.datetime.fromtimestamp(ts)

    In [44]: ts = time.mktime(t_obj)
    In [46]: datetime.datetime.fromtimestamp(ts)
    Out[46]: datetime.datetime(2018, 11, 14, 17, 21, 39)

12. timestamp ================> time
    time.localtime(ts)
    time.gmtime(ts)

        In [47]: time.localtime(ts)
        Out[47]: time.struct_time(tm_year=2018, tm_mon=11, tm_mday=14, tm_hour=17, tm_min=21, tm_sec=39, tm_wday=2, tm_yday=318, tm_isdst=0)
        
        In [48]: time.gmtime(ts)
        Out[48]: time.struct_time(tm_year=2018, tm_mon=11, tm_mday=14, tm_hour=9, tm_min=21, tm_sec=39, tm_wday=2, tm_yday=318, tm_isdst=0)
    

13. timestamp =================> string
    timestamp ------fromtimestamp---------------> datetime ----------------strftime---------------->string
    timestamp---------localtime-------------------> time-----------------------strftime------------------>string
    timestam-----------gmtime -------------------> time ----------------------strftime------------------>string

参考：
http://blog.sina.com.cn/s/blog_b09d460201018o0v.html
https://www.liaoxuefeng.com/wiki/0014316089557264a6b348958f449949df42a6d3a2e542c000/001431937554888869fb52b812243dda6103214cd61d0c2000