py 时间与日期

1. time模块

单位都是秒, 类型是float.
time.time()返回1970年至今的秒数.
time.clock()返回此次调用与第一次调用time.clock()之间的时间差.
time.sleep(x)线程挂起x秒.

2. datetime模块

官方参考文档, 点这里.
datetime.date 类,描述的是年月日.
datetime.datetime 类,描述的是年月日时分秒. 注意这两个datetime一个是模块一个是类, 易混淆.

2.1日期运算

date之间做减法, 得到的就是datedelta对象.
datetime.date()将datetime转为date.

today = datetime.date.today()  yestoday = today - datetime.timedelta(days=1)  tomorrow = today + datetime.timedelta(days=1) 

2.2转为字符串

date.strftime(format), format的常用值有:

• 年月日
  %Y 四位数的年份
  %m Month as a zero-padded decimal number
  %d Day of the month as a zero-padded decimal number.

• 时分秒
  %H Hour (24-hour clock) as a zero-padded decimal number.
  %M Minute as a zero-padded decimal number.
  %S Second as a zero-padded decimal number.

例子

• one

# date的例子import timeimport datetimefrom datetime import datetoday = date.today()    # datetime.date(2017, 8, 24)today == date.fromtimestamp(time.time())    # Truemy_birthday = date(today.year, 9, 3)if my_birthday < today:    my_birthday = my_birthday.replace(year=today.year + 1)my_birthday # datetime.date(2017, 9, 3)time_to_birthday = abs(my_birthday - today)time_to_birthday.days   #   20today.strftime('%Y%m%d') # '20170814'

• two

# datetime 的例子from datetime import datetime# 这个是datetime类的@classmethodd=datetime.now()print(type(d))print(d.strftime('%Y%m%d %H:%M:%S'))"""<class 'datetime.datetime'>20171103 10:17:55"""