python3: 數字日期和時間(2)

12.基本的日期與時間轉換

Q: 你須要執行簡單的時間轉換，好比天到秒，小時到分鐘等的轉換

A: 爲了執行不一樣時間單位的轉換和計算，請使用 datetime 模塊。 好比，爲了表示一個時間段，能夠建立一個 timedelta 實例，就像下面這樣：

>>> from datetime import timedelta
>>> a = timedelta(days=2, hours=6)
>>> b = timedelta(hours=4.5)
>>> c = a + b
>>> c.days
2
>>> c.seconds
37800
>>> c.seconds / 3600
10.5
>>> c.total_seconds() / 3600
58.5
>>>

若是你想表示指定的日期和時間，先建立一個 datetime 實例而後使用標準的數學運算來操做它們。好比：

>>> from datetime import datetime
>>> a = datetime(2012, 9, 23)
>>> print(a + timedelta(days=10))
2012-10-03 00:00:00
>>>
>>> b = datetime(2012, 12, 21)
>>> d = b - a
>>> d.days
89
>>> now = datetime.today()
>>> print(now)
2012-12-21 14:54:43.094063
>>> print(now + timedelta(minutes=10))
2012-12-21 15:04:43.094063
>>>

#datetime會自動處理閏年
>>> a = datetime(2012, 3, 1)
>>> b = datetime(2012, 2, 28)
>>> a - b
datetime.timedelta(2)
>>> (a - b).days
2
>>> c = datetime(2013, 3, 1)
>>> d = datetime(2013, 2, 28)
>>> (c - d).days
1
>>>

13. 計算最後一個週五的日期【第三方包python-dateutil 】

>>> from datetime import datetime
>>> from dateutil.relativedelta import relativedelta
>>> from dateutil.rrule import *
>>> d = datetime.now()
>>> print(d)
2012-12-23 16:31:52.718111

>>> # Next Friday
>>> print(d + relativedelta(weekday=FR))
2012-12-28 16:31:52.718111
>>>

>>> # Last Friday
>>> print(d + relativedelta(weekday=FR(-1)))
2012-12-21 16:31:52.718111
>>>

14. 計算當前月份的日期範圍

15. 字符串轉換爲日期

from datetime import datetime
def parse_ymd(s):
    year_s, mon_s, day_s = s.split('-')
    return datetime(int(year_s), int(mon_s), int(day_s))

 

16.結合時區的日期操做