Python学习入门（10）——时间
Python格式化日期时间的函数为datetime.datetime.strftime()；由字符串转为日期型的函数为：datetime.datetime.strptime()，两个函数都涉及日期时间的格式化字符串，列举如下：
%a Abbreviated weekday name
%A Full weekday name
%b Abbreviated month name
%B Full month name
%c Date and time representation appropriate for locale
%d Day of month as decimal number (01 - 31)
%f Micro seconds as decimal number (0 - 99999)
%H Hour in 24-hour format (00 - 23)
%I Hour in 12-hour format (01 - 12)
%j Day of year as decimal number (001 - 366)
%m Month as decimal number (01 - 12)
%M Minute as decimal number (00 - 59)
%p Current locale's A.M./P.M. indicator for 12-hour clock
%S Second as decimal number (00 - 59)
%U Week of year as decimal number, with Sunday as first day of week (00 - 51)
%w Weekday as decimal number (0 - 6; Sunday is 0)
%W Week of year as decimal number, with Monday as first day of week (00 - 51)
%x Date representation for current locale
%X Time representation for current locale
%y Year without century, as decimal number (00 - 99)
%Y Year with century, as decimal number
%z, %Z Time-zone name or abbreviation; no characters if time zone is unknown
%% Percent sign
示例：
#!/usr/bin/python
# it-homer in 2013
import sys
reload(sys)
sys.setdefaultencoding("utf-8")
import datetime
def format_time():
t = datetime.datetime.now()
print(t) # 2013-11-20 09:36:51.198680
t = datetime.datetime.now().strftime('%Y-%m-%d %H:%M:%S')
print(t) # 2013-11-20 09:39:16
t = datetime.datetime.now().strftime('%b-%d-%y %H:%M:%S')
print(t) # Nov-20-13 09:36:51
t = datetime.datetime.now().strftime('%b-%d-%Y %H:%M:%S')
print(t) # Nov-20-2013 09:36:51
# weekday
t = datetime.datetime.now().strftime('%a %A %U %W %w')
print(t) # Wed Wednesday 46 46 3
# month
t = datetime.datetime.now().strftime('%b %B')
print(t) # Nov November
# day
t = datetime.datetime.now().strftime('%d %j')
print(t) # 20 324
# date and time for locale
t = datetime.datetime.now().strftime('%c')
print(t) # Wed Nov 20 10:15:49 2013
# hour
t = datetime.datetime.now().strftime('%H %l')
print(t) # 10 10
# A.M/P.M
t = datetime.datetime.now().strftime('%p')
print(t) # AM
t = datetime.datetime.now().strftime('%x')
print(t) # 11/20/13
t = datetime.datetime.now().strftime('%X')
print(t) # 10:23:36
t = datetime.datetime.now().strftime('%x %X')
print(t) # 11/20/13 10:24:47
t = datetime.datetime.now().strftime('%z')
print(t) #
t = datetime.datetime.now().strftime('%Z')
print(t) #
# 字符串转换成datetime
t = datetime.datetime.strptime('Nov-20-13 09:42', '%b-%d-%y %H:%M')
print(t) # 2013-11-20 09:42:00
t = datetime.datetime(2013, 11, 20, 9, 42)
print(t) # 2013-11-20 09:42:00
# datetime转换成字符串
t = datetime.datetime.now().strftime('%b-%d-%y %H:%M:%S')
print(t) # Nov-20-13 10:26:40
if __name__ == "__main__":
format_time()
运行结果：
2013-11-20 10:29:26.456640
2013-11-20 10:29:26
Nov-20-13 10:29:26
Nov-20-2013 10:29:26
Wed Wednesday 46 46 3
Nov November
20 324
Wed Nov 20 10:29:26 2013
10 10
AM
11/20/13
10:29:26
11/20/13 10:29:26
2013-11-20 09:42:00
2013-11-20 09:42:00
Nov-20-13 10:29:26
timestamp <--> datetime
def main():
createtime = int(time.time()) # createtime = 1393316647
basefname2 = datetime.datetime.fromtimestamp(createtime).strftime('%Y-%m-%d %H:%M:%S')
print("timestamp -> datetime: %d : %s" % (createtime, basefname2))
nowtime = datetime.datetime.now()
future = nowtime + datetime.timedelta(minutes = 5)
print("datetime add: %s : %s" % (nowtime, future))
ts = time.mktime(future.timetuple())
print("datetime -> timestamp: %s : %d" % (future, ts))
运行结果：
timestamp -> datetime: 1393317675 : 2014-02-25 16:41:15
datetime add: 2014-02-25 16:41:15.900701 : 2014-02-25 16:46:15.900701
datetime -> timestamp: 2014-02-25 16:46:15.900701 : 1393317975
timestamp 转 datetime
" createtime ":1389151309
basefname2 = datetime.datetime.fromtimestamp( createtime ).strftime('%Y-%m-%d %H:%M:%S')
结果：
" createtime2 ":"2014-01-08 11:21:49"
参考： stackoverflow ，
完整示例：
def convet_cdate(ctime):
cday = 0
chour = 0
cminite = 0
csecond = 0
# ctime = '15秒前'
# ctime = '10分钟前'
# ctime = '2小时14分钟前'
# ctime = '1天24分钟前'
# ctime = '1天10小时24分钟前'
# ctime = '1天10小时24分钟15秒前'
ctime = '29分钟前'
# ctime = '23小时46分钟前'
if '天' in ctime:
cday = int(ctime.split('天')[0])
ctime = ctime.split('天')[1]
if '小时' in ctime:
chour = int(ctime.split('小时')[0])
ctime = ctime.split('小时')[1]
if '分钟' in ctime:
cminite = int(ctime.split('分钟')[0])
ctime = ctime.split('分钟')[1]
if '秒' in ctime:
csecond = int(ctime.split('秒')[0])
elapse_time = cday * 24 * 3600 + chour * 3600 + cminite * 60 + csecond
print("cday: " + str(cday) + "; chour: " + str(chour) + ", cminite: " + str(cminite) + "; csecond: " + str(csecond))
print("elapse_time: " + str(elapse_time))
ctime_now = int(time.time())
print("ctime_now: " + str(ctime_now))
print("elapse_now: " + str(ctime_now - elapse_time))
# timestamp -> datetime
result = datetime.datetime.fromtimestamp(ctime_now - elapse_time).strftime('%Y-%m-%d %H:%M:%S')
print("result: " + str(result))
计算两个日期差
def cal_date_delta(cls, dateStrFirst='20160912', dateStrLast='20660911'):
''' 计算日期相差的天数，返回整数
dateStrFirst : 起始日期，字符串格式，如 20160912
dateStrLast : 结束日期，如 20660911
'''
if isinstance(dateStrFirst, int): dateStrFirst = str(dateStrFirst)
if isinstance(dateStrLast, int): dateStrLast = str(dateStrLast)
d_first = datetime.datetime(int(dateStrFirst[0:4]), int(dateStrFirst[4:6]), int(dateStrFirst[6:8]))
d_last = datetime.datetime(int(dateStrLast[0:4]), int(dateStrLast[4:6]), int(dateStrLast[6:8]))
date_delta = (d_last - d_first).days
return date_delta
测试结果：
print 20160912, 20660911, YGDTime.cal_date_delta() # 20160912 20660911 18261 print "20161129", "20161202", YGDTime.cal_date_delta(20161128, 20161202) # 20161129 20161202 4 print 20161129, 20161202, YGDTime.cal_date_delta(20161128, 20171202) # 20161129 20161202 369
计算某个日期之前的日期
@classmethod
def cal_date_dtime(cls, dateStr=None, days=30):
''' 计算指定日期之前的某一天，计算之后的某一天days用负数
dateStr : 给定日期，如 20160912
'''
if dateStr is None:
dateStr = str(datetime.date.today())
else:
if isinstance(dateStr, int): dateStr = str(dateStr)
dateStr = '-'.join((dateStr[0:4], dateStr[4:6], dateStr[6:8]))
dateStr_date = datetime.datetime.strptime(dateStr, "%Y-%m-%d").date()
dateStr_date_lastStr = dateStr_date + datetime.timedelta(-days)
dateStr_date_lastInt = int(str(dateStr_date_lastStr).replace("-",""))
return dateStr_date_lastInt
测试结果：
print 20160912, 0, YGDTime.cal_date_dtime() # 20160912 0 20161104
print 20160912, 90, YGDTime.cal_date_dtime(20160912, -18261) # 20160912 90 20660911
print 20660911, 18261, YGDTime.cal_date_dtime('20660911', 18261) # 20660911 18261 20160912
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