6.3小节完成。
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XiongNeng
24
basic/datetime/basicdatetime.py
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24
basic/datetime/basicdatetime.py
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#!/usr/bin/env python
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# -*- encoding: utf-8 -*-
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"""
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Topic: sample
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Desc :
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"""
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from datetime import datetime, date, time, timedelta
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def my_datetime():
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today = datetime.now()
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print(today.ctime())
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oneday = timedelta(days=1)
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tomorrow = today + oneday
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print(tomorrow.ctime())
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# str to date
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dt = datetime.strptime('2012-01-12 12:12:12', '%Y-%m-%d %H:%M:%S')
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# date to str
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print(dt.strftime('%Y-%m-%d %H:%M:%S'))
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if __name__ == '__main__':
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my_datetime()
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@@ -1,20 +0,0 @@
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#!/usr/bin/env python
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# -*- encoding: utf-8 -*-
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"""
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Topic: sample
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Desc :
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"""
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import datetime
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__author__ = 'Xiong Neng'
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def my_datetime():
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today = datetime.datetime.now()
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print(today.ctime())
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oneday = datetime.timedelta(days=1)
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tomorrow = today + oneday
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print(tomorrow.ctime())
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if __name__ == '__main__':
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my_datetime()
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29
cookbook/c06/p03_simple_xml.py
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29
cookbook/c06/p03_simple_xml.py
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#!/usr/bin/env python
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# -*- encoding: utf-8 -*-
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"""
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Topic: 解析简单的XML
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Desc :
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"""
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from urllib.request import urlopen
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from xml.etree.ElementTree import parse
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def simple_xml():
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# Download the RSS feed and parse it
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u = urlopen('http://planet.python.org/rss20.xml')
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doc = parse(u)
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# Extract and output tags of interest
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for item in doc.iterfind('channel/item'):
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title = item.findtext('title')
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date = item.findtext('pubDate')
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link = item.findtext('link')
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print(title)
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print(date)
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print(link)
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print()
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if __name__ == '__main__':
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simple_xml()
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@@ -5,14 +5,137 @@
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----------
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问题
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----------
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todo...
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你想从一个简单的XML文档中提取数据。
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----------
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解决方案
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----------
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todo...
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可以使用 ``xml.etree.ElementTree`` 模块从简单的XML文档中提取数据。
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为了演示，假设你想解析Planet Python上的RSS源。下面是相应的代码：
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.. code-block:: python
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from urllib.request import urlopen
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from xml.etree.ElementTree import parse
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# Download the RSS feed and parse it
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u = urlopen('http://planet.python.org/rss20.xml')
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doc = parse(u)
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# Extract and output tags of interest
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for item in doc.iterfind('channel/item'):
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title = item.findtext('title')
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date = item.findtext('pubDate')
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link = item.findtext('link')
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print(title)
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print(date)
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print(link)
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print()
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运行上面的代码，输出结果类似这样：
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.. code-block:: python
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Steve Holden: Python for Data Analysis
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Mon, 19 Nov 2012 02:13:51 +0000
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http://holdenweb.blogspot.com/2012/11/python-for-data-analysis.html
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Vasudev Ram: The Python Data model (for v2 and v3)
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Sun, 18 Nov 2012 22:06:47 +0000
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http://jugad2.blogspot.com/2012/11/the-python-data-model.html
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Python Diary: Been playing around with Object Databases
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Sun, 18 Nov 2012 20:40:29 +0000
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http://www.pythondiary.com/blog/Nov.18,2012/been-...-object-databases.html
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Vasudev Ram: Wakari, Scientific Python in the cloud
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Sun, 18 Nov 2012 20:19:41 +0000
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http://jugad2.blogspot.com/2012/11/wakari-scientific-python-in-cloud.html
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Jesse Jiryu Davis: Toro: synchronization primitives for Tornado coroutines
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Sun, 18 Nov 2012 20:17:49 +0000
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http://feedproxy.google.com/~r/EmptysquarePython/~3/_DOZT2Kd0hQ/
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很显然，如果你想做进一步的处理，你需要替换 ``print()`` 语句来完成其他有趣的事。
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----------
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讨论
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----------
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todo...
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在很多应用程序中处理XML编码格式的数据是很常见的。
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不仅是因为XML在Internet上面已经被广泛应用于数据交换，
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同时它也是一种存储应用程序数据的常用格式(比如字处理，音乐库等)。
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接下来的讨论会先假定读者已经对XML基础比较熟悉了。
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在很多情况下，当使用XML来仅仅存储数据的时候，对应的文档结构非常紧凑并且直观。
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例如，上面例子中的RSS订阅源类似于下面的格式：
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.. code-block:: python
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<?xml version="1.0"?>
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<rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/">
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<channel>
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<title>Planet Python</title>
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<link>http://planet.python.org/</link>
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<language>en</language>
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<description>Planet Python - http://planet.python.org/</description>
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<item>
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<title>Steve Holden: Python for Data Analysis</title>
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<guid>http://holdenweb.blogspot.com/...-data-analysis.html</guid>
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<link>http://holdenweb.blogspot.com/...-data-analysis.html</link>
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<description>...</description>
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<pubDate>Mon, 19 Nov 2012 02:13:51 +0000</pubDate>
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</item>
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<item>
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<title>Vasudev Ram: The Python Data model (for v2 and v3)</title>
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<guid>http://jugad2.blogspot.com/...-data-model.html</guid>
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<link>http://jugad2.blogspot.com/...-data-model.html</link>
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<description>...</description>
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<pubDate>Sun, 18 Nov 2012 22:06:47 +0000</pubDate>
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</item>
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<item>
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<title>Python Diary: Been playing around with Object Databases</title>
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<guid>http://www.pythondiary.com/...-object-databases.html</guid>
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<link>http://www.pythondiary.com/...-object-databases.html</link>
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<description>...</description>
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<pubDate>Sun, 18 Nov 2012 20:40:29 +0000</pubDate>
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</item>
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...
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</channel>
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</rss>
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``xml.etree.ElementTree.parse()`` 函数解析整个XML文档并将其转换成一个文档对象。
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然后，你就能使用 ``find()`` 、``iterfind()`` 和 ``findtext()`` 等方法来搜索特定的XML元素了。
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这些函数的参数就是某个指定的标签名，例如 ``channel/item`` 或 ``title`` 。
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每次指定某个标签时，你需要遍历整个文档结构。每次搜索操作会从一个起始元素开始进行。
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同样，每次操作所指定的标签名也是起始元素的相对路径。
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例如，执行 ``doc.iterfind('channel/item')`` 来搜索所有在 ``channel`` 元素下面的 ``item`` 元素。
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``doc`` 代表文档的最顶层(也就是第一级的 ``rss`` 元素)。
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然后接下来的调用 ``item.findtext()`` 会从已找到的 ``item`` 元素位置开始搜索。
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``ElementTree`` 模块中的每个元素有一些重要的属性和方法，在解析的时候非常有用。
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``tag`` 属性包含了标签的名字，``text`` 属性包含了内部的文本，而 ``get()`` 方法能获取属性值。例如：
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.. code-block:: python
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>>> doc
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<xml.etree.ElementTree.ElementTree object at 0x101339510>
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>>> e = doc.find('channel/title')
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>>> e
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<Element 'title' at 0x10135b310>
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>>> e.tag
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'title'
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>>> e.text
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'Planet Python'
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>>> e.get('some_attribute')
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>>>
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有一点要强调的是 ``xml.etree.ElementTree`` 并不是XML解析的唯一方法。
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对于更高级的应用程序，你需要考虑使用 ``lxml`` 。它使用了和ElementTree同样的编程接口，
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因此上面的例子同样也适用于lxml。你只需要将刚开始的import语句换成 ``lxml.etree import parse`` 就行了。
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``lxml`` 完全遵循XML标准，并且速度也非常快，同时还支持验证，XSLT和XPath等特性。
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