Python date 类型转 datetime 类型

datetime to date

在 Python 中，通过 datetime 获取到日志的 date 类型比较简单, datetime 提供了 date() 方法

In [1]: from datetime import datetimeIn [2]: help(datetime.date)In [3]: datetime.now()Out[3]: datetime.datetime(2017, 6, 22, 10, 49, 22, 95457)In [4]: datetime.now().date()Out[4]: datetime.date(2017, 6, 22)

datetime date 比较

再看看下面一个例子

# coding:utf-8# python2.7# Convert date to datetime in Pythonfrom datetime import datetimetoday = datetime.now().date()todaytime = datetime.now()print today == todaytimeprint today > todaytime

运行之后这样的

# python datetime_date_comp.pyTraceback (most recent call last):  File "datetime_date_comp.py", line 8, in <module>    today > todaytimeTypeError: can't compare datetime.datetime to datetime.date

datetime 和 date 不能进行 大小比较, 就有一个把 date 类型转成 datetime 类型的需求了

date to datetime

下面是几种方式

from datetime import datetime, dated = date.today()print datetime.combine(d, datetime.min.time())print datetime.fromordinal(d.toordinal())print datetime(d.year, d.month, d.day)print datetime(*d.timetuple()[:-4])

simple test

In [8]: %time datetime(*d.timetuple()[:-4])CPU times: user 10 µs, sys: 0 ns, total: 10 µsWall time: 25 µsOut[8]: datetime.datetime(2017, 6, 22, 0, 0)In [9]: %time datetime(d.year, d.month, d.day)CPU times: user 5 µs, sys: 1 µs, total: 6 µsWall time: 16 µsOut[9]: datetime.datetime(2017, 6, 22, 0, 0)In [10]: %time datetime.fromordinal(d.toordinal())CPU times: user 6 µs, sys: 0 ns, total: 6 µsWall time: 8.11 µsOut[10]: datetime.datetime(2017, 6, 22, 0, 0)In [11]: %time datetime.combine(d, datetime.min.time())CPU times: user 8 µs, sys: 4 µs, total: 12 µsWall time: 11 µsOut[11]: datetime.datetime(2017, 6, 22, 0, 0)

看起来 datetime(d.year, d.month, d.day) 这种方式更好一些。