python日期与时间函数实例详解

#-*- coding: utf-8 -*-
import datetime

#给定日期向后N天的日期
def dateadd_day(days):
    d1 = datetime.datetime.now()
    d3 = d1 + datetime.timedelta(days)
    return d3

#昨天
def getYesterday():
    today = datetime.date.today()
    oneday = datetime.timedelta(days=1)
    yesterday = today - oneday
    return yesterday

#今天
def getToday():
    return datetime.date.today()

#获取给定参数的前几天的日期，返回一个list
def getDaysBefore(num):
    today = datetime.date.today()
    oneday = datetime.timedelta(days=1)
    li = []
    for i in range(0, num):
        #今天减一天，一天一天减
        today = today - oneday
        #把日期转换成字符串
        li.append(datetostr(today))
    return li

#将字符串转换成datetime类型
def strtodatetime(datestr, format):
    return datetime.datetime.strptime(datestr, format)

#时间转换成字符串,格式为2015-02-02
def datetostr(date):
    return str(date)[0:10]

#时间转换成字符串,格式为2015-02-02
def datetostr_secod(date):
    return str(date)[0:19]

#两个日期相隔多少天，例：2015-2-04和2015-3-1
def datediff(beginDate, endDate):
    format = "%Y-%m-%d"
    bd = strtodatetime(beginDate, format)
    ed = strtodatetime(endDate, format)
    oneday = datetime.timedelta(days=1)
    count = 0
    while bd != ed:
        ed = ed - oneday
        count += 1
    return count

#两个日期之间相差的秒
def datediff_seconds(beginDate, endDate):
    format = "%Y-%m-%d %H:%M:%S"
    if " " not in beginDate or ':' not in beginDate:
        bformat = "%Y-%m-%d"
    else:
        bformat = format
    if " " not in endDate or ':' not in endDate:
        eformat = "%Y-%m-%d"
    else:
        eformat = format
    starttime = strtodatetime(beginDate, bformat)
    endtime = strtodatetime(endDate, eformat)
    ret = endtime - starttime
    return ret.days * 86400 + ret.seconds

#获取两个时间段的所有时间,返回list
def getDays(beginDate, endDate):
    format = "%Y-%m-%d"
    begin = strtodatetime(beginDate, format)
    oneday = datetime.timedelta(days=1)
    num = datediff(beginDate, endDate) + 1
    li = []
    for i in range(0, num):
        li.append(datetostr(begin))
        begin = begin + oneday
    return li

#获取当前年份 是一个字符串
def getYear(date=datetime.date.today()):
    return str(date)[0:4]

#获取当前月份 是一个字符串
def getMonth(date=datetime.date.today()):
    return str(date)[5:7]

#获取当前天 是一个字符串
def getDay(date=datetime.date.today()):
    return str(date)[8:10]

#获取当前小时 是一个字符串
def getHour(date=datetime.datetime.now()):
    return str(date)[11:13]

#获取当前分钟 是一个字符串
def getMinute(date=datetime.datetime.now()):
    return str(date)[14:16]

#获取当前秒 是一个字符串
def getSecond(date=datetime.datetime.now()):
    return str(date)[17:19]

def getNow():
    return datetime.datetime.now()

print dateadd_day(10)
#2015-02-14 16:41:13.275000

print getYesterday()
#2015-02-03

print getToday()
#2015-02-04

print getDaysBefore(3)
#['2015-02-03', '2015-02-02', '2015-02-01']

print datediff('2015-2-01', '2015-10-05')
#246

print datediff_seconds('2015-02-04', '2015-02-05')
#86400

print datediff_seconds('2015-02-04 22:00:00', '2015-02-05')
#7200

print getDays('2015-2-03', '2015-2-05')
#['2015-02-03', '2015-02-04', '2015-02-05']

print datetostr_secod(getNow())
#2015-02-04 16:46:47

print str(getYear(dateadd_day(-50))) + '-'
    + getMonth() + '-'
    + getDay() + ' '
    + getHour() + ':'
    + getMinute() + ':'
    + getSecond()
#2014-02-04 16:59:04

print getNow()
#2015-02-04 16:46:47.454000