如何在Python中修改atom/rss源？

Question

我想在Python中做以下几件事：

1. 获取一个数据源
2. 往这个数据源里添加一些数据
3. 把修改过的数据源重新发布出去

Feedparser在解析数据方面表现不错，但似乎没有提供从FeedParserDict对象创建XML文档的方法。

有没有更简单的方法，不用自己写一个组合函数呢？

Answer 1

你可以使用 lxml 库，或者自己写一个，利用 Python 的模板库。

• 自己写一个：将 FeedParser 对象转换为 Atom 格式
• 使用 lxml 的例子：用 lxml 和循环在 Python 中创建 XML RSS

Answer 2

我自己写了一个Atom 1.0的序列化器，使用了Django的模板引擎。我尽量把它做得尽可能完整，这样其他人也可以重复使用。

import feedparser
from django.template import Template
d = feedparser.parse("http://example.com/feed.xml") # creating a FeedParserDict
# ... do stuff with d
t = Template(the_stuff_below) # compiling the template
output_atom_document = t.render(d)

要注意的是，feedparser的清理工作只通过 feedparser.parse() 来完成，所以你传给 FeedParserDict 的任何内容，如果需要的话，必须提前清理干净。

如果你想用这个来修改一个信息源，记得要更改id值（每个信息源一个，每个条目一个），因为这些id应该是唯一的。

<?xml version="1.0" encoding="{{ encoding }}"?>
<feed xmlns="http://www.w3.org/2005/Atom">
    <title type="{{ feed.title_detail.type }}" xml:lang="{{ feed.title_detail.language }}" xml:base="{{ feed.title_detail.base }}">{{ feed.title|escape }}</title>
{% for link in feed.links %}
    <link rel="{{ link.rel }}" type="{{ link.type }}" href="{{ link.href }}" title="{{ link.title }}"/>
{% endfor %}
    <subtitle type="{{ feed.subtitle_detail.type }}" xml:lang="{{ feed.subtitle_detail.language }}" xml:base="{{ feed.subtitle_detail.base }}">{{ feed.subtitle|escape }}</subtitle>
    <rights type="{{ feed.rights_detail.type }}" xml:lang="{{ feed.rights_detail.language }}" xml:base="{{ feed.rights_detail.base }}">{{ feed.rights|escape }}</rights>
    <generator uri="{{ feed.generator_detail.href }}" version="{{ feed.generator_detail.version }}">{{ feed.generator }}</generator>
    <info type="{{ feed.info_detail.type }}" xml:lang="{{ feed.info_detail.language }}" xml:base="{{ feed.info_detail.base }}">{{ feed.info|escape }}</info>
    <updated>{{ feed.updated }}</updated>
    <id>{{ feed.id }}</id>
    <author>
        <name>{{ feed.author }}</name>
        <uri>{{ feed.author_detail.href }}</uri>
        <email>{{ feed.author_detail.email }}</email>
    </author>
{% for contributor in feed.contributors %}
    <contributor>
        <name>{{ contributor }}</name>
        <uri>{{ contributor_detail.href }}</uri>
        <email>{{ contributor_detail.email }}</email>
    </contributor>
{% endfor %}
    <image>
        <title>{{ feed.image.title }}</title>
        <url>{{ feed.image.href }}</url>
        <link>{{ feed.image.link }}</link>
        <width>{{ feed.image.width }}</width>
        <height>{{ feed.image.height }}</height>
        <description>{{ feed.image.description }}</description>
    </image>
    <icon>{{ feed.icon }}</icon>
    <!-- not part of Atom 1.0: feed.textinput -->
    <!-- not part of Atom 1.0: feed.cloud -->
    <publisher>
        <name>{{ feed.publisher }}</name>
        <uri>{{ feed.publisher_detail.href }}</uri>
        <email>{{ feed.publisher_detail.email }}</email>
    </publisher>
{% for tag in feed.tags %}
    <tag>
        <term>{{ tag.term }}</term>
        <scheme>{{ tag.scheme }}</scheme>
        <label>{{ tag.label }}</label>
    </tag>
{% endfor %}
    <language>{{ feed.language }}</language>
    <!-- not part of Atom 1.0: feed.license -->
    <!-- not part of Atom 1.0: feed.errorreportsto -->
{% for entry in entries %}
    <entry>
        <title type="{{ entry.title_detail.type }}" xml:lang="{{ entry.title_detail.language }}" xml:base="{{ entry.title_detail.base }}">{{ entry.title|escape }}</title>
    {% for link in entry.links %}
        <link rel="{{ link.rel }}" type="{{ link.type }}" href="{{ link.href }}" title="{{ link.title }}"/>
    {% endfor %}
        <summary type="{{ entry.summary_detail.type }}" xml:lang="{{ entry.summary_detail.language }}" xml:base="{{ entry.summary_detail.base }}">{{ entry.summary|escape }}</summary>
    {% for content in entry.content %}
        <content type="{{ content.type }}" xml:lang="{{ content.language }}" xml:base="{{ content.base }}">{{ content.value|escape }}</content>
    {% endfor %}
        <published>{{ entry.published }}</published>
        <updated>{{ entry.updated }}</updated>
        <created>{{ entry.created }}</created>
        <!-- not part of Atom 1.0: entry.expired -->
        <id>{{ entry.id }}</id>
        <author>
            <name>{{ entry.author }}</name>
            <uri>{{ entry.author_detail.href }}</uri>
            <email>{{ entry.author_detail.email }}</email>
        </author>
    {% for contributor in entry.contributors %}
        <contributor>
            <name>{{ contributor }}</name>
            <uri>{{ contributor_detail.href }}</uri>
            <email>{{ contributor_detail.email }}</email>
        </contributor>
    {% endfor %}
    {% for enclosure in entry.enclosures %}
        <link rel="enclosure" href="{{ enclosure.href }}" length="{{ enclosure.length }}" type="{{ enclosure.type }}"/>
    {% endfor %}
        <publisher>
            <name>{{ entry.publisher }}</name>
            <uri>{{ entry.publisher_detail.href }}</uri>
            <email>{{ entry.publisher_detail.email }}</email>
        </publisher>
    {% for tag in entry.tags %}
        <tag>
            <term>{{ tag.term }}</term>
            <scheme>{{ tag.scheme }}</scheme>
            <label>{{ tag.label }}</label>
        </tag>
    {% endfor %}
    <source>
        <author>
            <name>{{ entry.source.author }}</name>
            <uri>{{ entry.source.author_detail.href }}</uri>
            <email>{{ entry.source.author_detail.email }}</email>
        </author>
    {% for contributor in entry.source.contributors %}
        <contributor>
            <name>{{ contributor }}</name>
            <uri>{{ contributor_detail.href }}</uri>
            <email>{{ contributor_detail.email }}</email>
        </contributor>
    {% endfor %}
        <icon>{{ entry.source.icon }}</icon>
        <id>{{ entry.source.id }}</id>
    {% for link in entry.source.links %}
        <link rel="{{ link.rel }}" type="{{ link.type }}" href="{{ link.href }}" title="{{ link.title }}"/>
    {% endfor %}
        <logo>{{ entry.source.logo }}</logo>
        <rights type="{{ entry.source.rights_detail.type }}" xml:lang="{{ entry.source.rights_detail.language }}" xml:base="{{ entry.source.rights_detail.base }}">{{ entry.source.rights|escape }}</rights>
        <subtitle type="{{ entry.source.subtitle_detail.type }}" xml:lang="{{ entry.source.subtitle_detail.language }}" xml:base="{{ entry.source.subtitle_detail.base }}">{{ entry.source.subtitle|escape }}</subtitle>
        <title type="{{ entry.source.title_detail.type }}" xml:lang="{{ entry.source.title_detail.language }}" xml:base="{{ entry.source.title_detail.base }}">{{ entry.source.title|escape }}</title>
        <updated>{{ entry.source.updated }}</updated>
    </source>
    <!-- not part of Atom 1.0: entry.comments -->
    <!-- not part of Atom 1.0: entry.license -->
    </entry>
{% endfor %}
    <!-- meaningless: version (this is Atom 1.0) -->
    <!-- meaningless: namespaces (namespace set to "http://www.w3.org/2005/Atom" in the <feed> tag) -->
    <!-- somewhere else: encoding (in the XML declaration) -->
    <!-- meaningless: status (HTTP status) -->
    <!-- meaningless: href (present if server redirect when fetching the original feed) -->
    <!-- meaningless: etag (part of HTTP headers) -->
    <!-- meaningless: modified (part of HTTP headers) -->
    <!-- meaningless: headers (HTTP headers) -->
    <!-- meaningless: bozo (set to 1 if not well-formed XML) -->
    <!-- meaningless: bozo_exception -->
</feed>