python - Python datetime:tz inside 方法和 .replace(tzinfo=) 之间的区别
问题描述
我最近修复了一个错误,但仍然不知道为什么会发生。我有以下将时间戳(纪元)转换为 Django 模型中的日期时间字段:
our_timezone = pytz.timezone("Asia/Jerusalem")
# e13 is used for true division
final_dict["published_date"] = datetime.datetime.fromtimestamp(
float(article_as_dict["publish_date"]) / 1e3).replace(tzinfo=our_timezone)
上面返回了一个 datetime 对象,它总是比真正的纪元时间(在我们的时区)晚39 分钟。
我设法通过删除来修复它replace
,而是将时区放在fromtimestamp
方法中:
final_dict["published_date"] = datetime.datetime.fromtimestamp(
float(article_as_dict["publish_date"]) / 1e3, tz=our_timezone)
tz=our_timezone
那么指定方法内部fromtimestamp
和.replace(tzinfo=our_timezone)
创建对象后做的有什么区别呢?为什么.replace
返回错误的时间?
解决方案
>>> datetime.fromtimestamp(1000000000).replace(tzinfo=our_timezone)
datetime.datetime(2001, 9, 9, 3, 46, 40, tzinfo=<DstTzInfo 'Asia/Jerusalem' LMT+2:21:00 STD>)
>>> datetime.fromtimestamp(1000000000, tz=our_timezone)
datetime.datetime(2001, 9, 9, 4, 46, 40, tzinfo=<DstTzInfo 'Asia/Jerusalem' IDT+3:00:00 DST>)
请注意第一种情况下的奇数时区偏移。
时区是多个偏移量的捆绑。时区偏移随时间而变化。它不仅会根据夏季和冬季时间在一年内发生变化,而且在修改和更新时区数据时也会发生历史变化。您可以检查时区对象以获取一些有趣的历史数据,这些数据可以追溯到几十年前:
>>> our_timezone._utc_transition_times
[datetime.datetime(1, 1, 1, 0, 0), datetime.datetime(1901, 12, 13, 20, 45, 52), datetime.datetime(1917, 12, 31, 21, 39, 20), datetime.datetime(1940, 5, 31, 22, 0), datetime.datetime(1942, 10, 31, 21, 0), datetime.datetime(1943, 4, 1, 0, 0), datetime.datetime(1943, 10, 31, 21, 0), datetime.datetime(1944, 3, 31, 22, 0), datetime.datetime(1944, 10, 31, 21, 0), datetime.datetime(1945, 4, 15, 22, 0), datetime.datetime(1945, 10, 31, 23, 0), datetime.datetime(1946, 4, 16, 0, 0), datetime.datetime(1946, 10, 31, 21, 0), datetime.datetime(1948, 5, 22, 22, 0), datetime.datetime(1948, 8, 31, 20, 0), datetime.datetime(1948, 10, 31, 23, 0), datetime.datetime(1949, 4, 30, 22, 0), datetime.datetime(1949, 10, 31, 23, 0), datetime.datetime(1950, 4, 15, 22, 0), datetime.datetime(1950, 9, 15, 0, 0), datetime.datetime(1951, 3, 31, 22, 0), datetime.datetime(1951, 11, 11, 0, 0), datetime.datetime(1952, 4, 20, 0, 0), datetime.datetime(1952, 10, 19, 0, 0), datetime.datetime(1953, 4, 12, 0, 0), datetime.datetime(1953, 9, 13, 0, 0), datetime.datetime(1954, 6, 12, 22, 0), datetime.datetime(1954, 9, 11, 21, 0), datetime.datetime(1955, 6, 11, 0, 0), datetime.datetime(1955, 9, 10, 21, 0), datetime.datetime(1956, 6, 2, 22, 0), datetime.datetime(1956, 9, 30, 0, 0), datetime.datetime(1957, 4, 29, 0, 0), datetime.datetime(1957, 9, 21, 21, 0), datetime.datetime(1974, 7, 6, 22, 0), datetime.datetime(1974, 10, 12, 21, 0), datetime.datetime(1975, 4, 19, 22, 0), datetime.datetime(1975, 8, 30, 21, 0), datetime.datetime(1985, 4, 13, 22, 0), datetime.datetime(1985, 9, 14, 21, 0), datetime.datetime(1986, 5, 17, 22, 0), datetime.datetime(1986, 9, 6, 21, 0), datetime.datetime(1987, 4, 14, 22, 0), datetime.datetime(1987, 9, 12, 21, 0), datetime.datetime(1988, 4, 9, 22, 0), datetime.datetime(1988, 9, 3, 21, 0), datetime.datetime(1989, 4, 29, 22, 0), datetime.datetime(1989, 9, 2, 21, 0), datetime.datetime(1990, 3, 24, 22, 0), datetime.datetime(1990, 8, 25, 21, 0), datetime.datetime(1991, 3, 23, 22, 0), datetime.datetime(1991, 8, 31, 21, 0), datetime.datetime(1992, 3, 28, 22, 0), datetime.datetime(1992, 9, 5, 21, 0), datetime.datetime(1993, 4, 1, 22, 0), datetime.datetime(1993, 9, 4, 21, 0), datetime.datetime(1994, 3, 31, 22, 0), datetime.datetime(1994, 8, 27, 21, 0), datetime.datetime(1995, 3, 30, 22, 0), datetime.datetime(1995, 9, 2, 21, 0), datetime.datetime(1996, 3, 14, 22, 0), datetime.datetime(1996, 9, 15, 21, 0), datetime.datetime(1997, 3, 20, 22, 0), datetime.datetime(1997, 9, 13, 21, 0), datetime.datetime(1998, 3, 19, 22, 0), datetime.datetime(1998, 9, 5, 21, 0), datetime.datetime(1999, 4, 2, 0, 0), datetime.datetime(1999, 9, 2, 23, 0), datetime.datetime(2000, 4, 14, 0, 0), datetime.datetime(2000, 10, 5, 22, 0), datetime.datetime(2001, 4, 8, 23, 0), datetime.datetime(2001, 9, 23, 22, 0), datetime.datetime(2002, 3, 28, 23, 0), datetime.datetime(2002, 10, 6, 22, 0), datetime.datetime(2003, 3, 27, 23, 0), datetime.datetime(2003, 10, 2, 22, 0), datetime.datetime(2004, 4, 6, 23, 0), datetime.datetime(2004, 9, 21, 22, 0), datetime.datetime(2005, 4, 1, 0, 0), datetime.datetime(2005, 10, 8, 23, 0), datetime.datetime(2006, 3, 31, 0, 0), datetime.datetime(2006, 9, 30, 23, 0), datetime.datetime(2007, 3, 30, 0, 0), datetime.datetime(2007, 9, 15, 23, 0), datetime.datetime(2008, 3, 28, 0, 0), datetime.datetime(2008, 10, 4, 23, 0), datetime.datetime(2009, 3, 27, 0, 0), datetime.datetime(2009, 9, 26, 23, 0), datetime.datetime(2010, 3, 26, 0, 0), datetime.datetime(2010, 9, 11, 23, 0), datetime.datetime(2011, 4, 1, 0, 0), datetime.datetime(2011, 10, 1, 23, 0), datetime.datetime(2012, 3, 30, 0, 0), datetime.datetime(2012, 9, 22, 23, 0), datetime.datetime(2013, 3, 29, 0, 0), datetime.datetime(2013, 10, 26, 23, 0), datetime.datetime(2014, 3, 28, 0, 0), datetime.datetime(2014, 10, 25, 23, 0), datetime.datetime(2015, 3, 27, 0, 0), datetime.datetime(2015, 10, 24, 23, 0), datetime.datetime(2016, 3, 25, 0, 0), datetime.datetime(2016, 10, 29, 23, 0), datetime.datetime(2017, 3, 24, 0, 0), datetime.datetime(2017, 10, 28, 23, 0), datetime.datetime(2018, 3, 23, 0, 0), datetime.datetime(2018, 10, 27, 23, 0), datetime.datetime(2019, 3, 29, 0, 0), datetime.datetime(2019, 10, 26, 23, 0), datetime.datetime(2020, 3, 27, 0, 0), datetime.datetime(2020, 10, 24, 23, 0), datetime.datetime(2021, 3, 26, 0, 0), datetime.datetime(2021, 10, 30, 23, 0), datetime.datetime(2022, 3, 25, 0, 0), datetime.datetime(2022, 10, 29, 23, 0), datetime.datetime(2023, 3, 24, 0, 0), datetime.datetime(2023, 10, 28, 23, 0), datetime.datetime(2024, 3, 29, 0, 0), datetime.datetime(2024, 10, 26, 23, 0), datetime.datetime(2025, 3, 28, 0, 0), datetime.datetime(2025, 10, 25, 23, 0), datetime.datetime(2026, 3, 27, 0, 0), datetime.datetime(2026, 10, 24, 23, 0), datetime.datetime(2027, 3, 26, 0, 0), datetime.datetime(2027, 10, 30, 23, 0), datetime.datetime(2028, 3, 24, 0, 0), datetime.datetime(2028, 10, 28, 23, 0), datetime.datetime(2029, 3, 23, 0, 0), datetime.datetime(2029, 10, 27, 23, 0), datetime.datetime(2030, 3, 29, 0, 0), datetime.datetime(2030, 10, 26, 23, 0), datetime.datetime(2031, 3, 28, 0, 0), datetime.datetime(2031, 10, 25, 23, 0), datetime.datetime(2032, 3, 26, 0, 0), datetime.datetime(2032, 10, 30, 23, 0), datetime.datetime(2033, 3, 25, 0, 0), datetime.datetime(2033, 10, 29, 23, 0), datetime.datetime(2034, 3, 24, 0, 0), datetime.datetime(2034, 10, 28, 23, 0), datetime.datetime(2035, 3, 23, 0, 0), datetime.datetime(2035, 10, 27, 23, 0), datetime.datetime(2036, 3, 28, 0, 0), datetime.datetime(2036, 10, 25, 23, 0), datetime.datetime(2037, 3, 27, 0, 0), datetime.datetime(2037, 10, 24, 23, 0)]
随着datetime.fromtimestamp(1000000000)
您创建一个简单的时间戳,一个没有时区信息的时间戳。然后,您只需将时区对象附加到它replace
。这只会导致 Python 使用该时区对象中的许多偏移对象中的第一个,这导致与一百年前的偏移量出现奇数。
但是,将时区对象作为“上下文信息”fromtimestamp
直接提供给该方法可以选择适用于时间戳的正确偏移量并正确生成一致的时间戳对象。
事后您也可以这样做astimezone
:
>>> datetime.fromtimestamp(1000000000).astimezone(our_timezone)
datetime.datetime(2001, 9, 9, 4, 46, 40, tzinfo=<DstTzInfo 'Asia/Jerusalem' IDT+3:00:00 DST>)
此方法还可以智能地选择适用的偏移量。
简而言之:replace
==愚蠢,只需覆盖原始数据,fromtimestamp
==astimezone
聪明,知道如何使用时区。
推荐阅读
- javascript - 尝试使用 javascript/jquery 将我的元素放入容器/包装器中
- machine-learning - 如何减少多元线性回归的均方根误差
- java - 代码如何与正在运行的服务连接?
- php - 在 php 中,递增数字是错误的
- android - 适用于 Android 和 Windows Embedded 的 Xamarin 跨平台后台服务
- mysql - 来自 Mysql 全文搜索的精确匹配搜索
- vba - MS Access Project 内存不足错误
- operating-system - 临界区进程中断
- php - 一列的总和作为phpmyadmin中的另一列
- git - 尽管我的 .gitignore,为什么我的配置文件仍被签入?