时间的三种格式：
- 时间戳(timestamp)：
通常来说，时间戳表示的是从1970年1月1日00:00:00开始按秒计算的偏移量。
例子：（1510303620.0）float类型 - 格式化的时间字符串(Format String)
例子：'2017-11-10 16:40:33' - 结构化的时间(struct_time)
struct_time元组共有9个元素共九个元素:(年，月，日，时，分，秒，一年中第几周，一年中第几天，夏令时)
示例
import time
time.time() #时间戳:1487130156.419527
time.strftime("%Y-%m-%d %X") #格式化的时间字符串:'2017-02-15 11:40:53'
time.localtime() #本地时区的struct_time
time.gmtime() #UTC时区（0时区）的struct_time
格式化字符串的时间格式
%a Locale’s abbreviated weekday name.
%A Locale’s full weekday name.
%b Locale’s abbreviated month name.
%B Locale’s full month name.
%c Locale’s appropriate date and time representation.
%d Day of the month as a decimal number [01,31].
%H Hour (24-hour clock) as a decimal number [00,23].
%I Hour (12-hour clock) as a decimal number [01,12].
%j Day of the year as a decimal number [001,366].
%m Month as a decimal number [01,12].
%M Minute as a decimal number [00,59].
%p Locale’s equivalent of either AM or PM. (1)
%S Second as a decimal number [00,61]. (2)
%U Week number of the year (Sunday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Sunday are considered to be in week 0. (3)
%w Weekday as a decimal number [0(Sunday),6].
%W Week number of the year (Monday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Monday are considered to be in week 0. (3)
%x Locale’s appropriate date representation.
%X Locale’s appropriate time representation.
%y Year without century as a decimal number [00,99].
%Y Year with century as a decimal number.
%z Time zone offset indicating a positive or negative time difference from UTC/GMT of the form +HHMM or -HHMM, where H represents decimal hour digits and M represents decimal minute digits [-23:59, +23:59].
%Z Time zone name (no characters if no time zone exists).
%% A literal '%' character.
转换格式
image.png
#localtime([secs])
#将一个时间戳转换为当前时区的struct_time。secs参数未提供，则以当前时间为准。
time.localtime()
#time.struct_time(tm_year=2017, tm_mon=11, tm_mday=10, tm_hour=16, tm_min=56, tm_sec=41, tm_wday=4, tm_yday=314, tm_isdst=0)
time.localtime(1473525444.037215)
#time.struct_time(tm_year=2016, tm_mon=9, tm_mday=11, tm_hour=0, tm_min=37, tm_sec=24, tm_wday=6, tm_yday=255, tm_isdst=0)
# gmtime([secs]) 和localtime()方法类似，gmtime()方法是将一个时间戳转换为UTC时区（0时区）的struct_time。
# mktime(t) : 将一个struct_time转化为时间戳。
print(time.mktime(time.localtime()))#1473525749.0
# strftime(format[, t]) : 把一个代表时间的元组或者struct_time
print(time.strftime("%Y-%m-%d %X", time.localtime()))#2016-09-11 00:49:56
# time.strptime(string[, format])
# 把一个格式化时间字符串转化为struct_time。实际上它和strftime()是逆操作。
# 在这个函数中，format默认为："%a %b %d %H:%M:%S %Y"。
print(time.strptime('2011-05-05 16:37:06', '%Y-%m-%d %X'))
#time.struct_time(tm_year=2011, tm_mon=5, tm_mday=5, tm_hour=16, tm_min=37, tm_sec=6,tm_wday=3, tm_yday=125, tm_isdst=-1)
image.png
# asctime([t]) : 把一个表示时间的元组或者struct_time表示为这种形式：'Sun Jun 20 23:21:05 1993'。
# 如果没有参数，将会将time.localtime()作为参数传入。
print(time.asctime())#Sun Sep 11 00:43:43 2016
# ctime([secs]) : 把一个时间戳（按秒计算的浮点数）转化为time.asctime()的形式。如果参数未给或者为None的时候，将会默认time.time()为参数
# 它的作用相当于time.asctime(time.localtime(secs))。
print(time.ctime()) # Sun Sep 11 00:46:38 2016
print(time.ctime(time.time())) # Sun Sep 11 00:46:38 2016
#--------------------------其他用法
# sleep(secs) ：线程推迟指定的时间运行，单位为秒。
datetime模块
import datetime
#时间加减
# print(datetime.datetime.now()) #返回 2016-08-19 12:47:03.941925
# print(datetime.date.fromtimestamp(time.time()) ) # 时间戳直接转成日期格式 2016-08-19
# print(datetime.datetime.now() + datetime.timedelta(days=3)) #当前时间+3天
# print(datetime.datetime.now() + datetime.timedelta(days=-3)) #当前时间-3天
# print(datetime.datetime.now() + datetime.timedelta(hours=3)) #当前时间+3小时
# print(datetime.datetime.now() + datetime.timedelta(minutes=30)) #当前时间+30分
# 时间替换
# c_time = datetime.datetime.now()
# print(c_time.replace(minute=3,hour=2))