python - 使用Python进行基本xml解析

我正在通过Flickr的API从Flickr中提取图像数据，并且打印出的是几千个看起来像这样的xml对象：

<photo accuracy="15" context="0" dateupload="1398279194" farm="8" geo_is_contact="0" geo_is_family="0" geo_is_friend="0" geo_is_public="1" height_n="320" id="13986079375" isfamily="0" isfriend="0" ispublic="1" latitude="41.828482" license="0" longitude="-87.624506" owner="100231432@N02" pathalias="perspectivesschools" place_id="cF8n.mJTWrhYf0uBEw" secret="f46eef0b1d" server="7308" title="Sean Gallagher, Pulitzer Photojournalist visits MSA" url_n="https://farm8.staticflickr.com/7308/13986079375_f46eef0b1d_n.jpg" width_n="213" woeid="28297331" />
<photo accuracy="12" context="0" dateupload="1394558054" farm="4" geo_is_contact="0" geo_is_family="0" geo_is_friend="0" geo_is_public="1" height_n="213" id="13086071753" isfamily="0" isfriend="0" ispublic="1" latitude="51.451914" license="2" longitude="-0.122882" owner="96189004@N04" pathalias="" place_id="JYdWRftQUbMvFA" secret="265103ac38" server="3040" title="" url_n="https://farm4.staticflickr.com/3040/13086071753_265103ac38_n.jpg" width_n="320" woeid="13978" />
<photo accuracy="12" context="0" dateupload="1394558019" farm="8" geo_is_contact="0" geo_is_family="0" geo_is_friend="0" geo_is_public="1" height_n="213" id="13086343854" isfamily="0" isfriend="0" ispublic="1" latitude="51.451914" license="2" longitude="-0.122882" owner="96189004@N04" pathalias="" place_id="JYdWRftQUbMvFA" secret="a6858f84d2" server="7451" title="" url_n="https://farm8.staticflickr.com/7451/13086343854_a6858f84d2_n.jpg" width_n="320" woeid="13978" />

现在，我想一次运行提取属性“ lat”和“ long”的数据。另一个是属性“ url_n”的数据。如何在Python中做到这一点？我没有解析xml数据的经验，也不知道从哪里开始。

非常感谢！

最佳答案

使用lxml

虽然Python中有多个与XML相关的软件包， stdlib，我更喜欢使用lxml
它提供了我需要的所有东西（良好的XPath支持，模式验证等），我更喜欢保留数字
我使用的包装数量很少。

对于来自Flickr的xml文档，解决方案可能看起来像

脚本flickr.py

from lxml import etree
xmllines = """
<photo accuracy="15" context="0" dateupload="1398279194" farm="8" geo_is_contact="0" geo_is_family="0" geo_is_friend="0" geo_is_public="1" height_n="320" id="13986079375" isfamily="0" isfriend="0" ispublic="1" latitude="41.828482" license="0" longitude="-87.624506" owner="100231432@N02" pathalias="perspectivesschools" place_id="cF8n.mJTWrhYf0uBEw" secret="f46eef0b1d" server="7308" title="Sean Gallagher, Pulitzer Photojournalist visits MSA" url_n="https://farm8.staticflickr.com/7308/13986079375_f46eef0b1d_n.jpg" width_n="213" woeid="28297331" />
<photo accuracy="12" context="0" dateupload="1394558054" farm="4" geo_is_contact="0" geo_is_family="0" geo_is_friend="0" geo_is_public="1" height_n="213" id="13086071753" isfamily="0" isfriend="0" ispublic="1" latitude="51.451914" license="2" longitude="-0.122882" owner="96189004@N04" pathalias="" place_id="JYdWRftQUbMvFA" secret="265103ac38" server="3040" title="" url_n="https://farm4.staticflickr.com/3040/13086071753_265103ac38_n.jpg" width_n="320" woeid="13978" />
<photo accuracy="12" context="0" dateupload="1394558019" farm="8" geo_is_contact="0" geo_is_family="0" geo_is_friend="0" geo_is_public="1" height_n="213" id="13086343854" isfamily="0" isfriend="0" ispublic="1" latitude="51.451914" license="2" longitude="-0.122882" owner="96189004@N04" pathalias="" place_id="JYdWRftQUbMvFA" secret="a6858f84d2" server="7451" title="" url_n="https://farm8.staticflickr.com/7451/13086343854_a6858f84d2_n.jpg" width_n="320" woeid="13978" />
"""

for line in xmllines.strip().splitlines():
    doc = etree.fromstring(line)
    urls = doc.xpath("/photo/@url_n")
    if urls:
        url = urls[0]
        print url
    else:
        print "---no attribute url_n was found---"

将输出：

$ python flickr.py
https://farm8.staticflickr.com/7308/13986079375_f46eef0b1d_n.jpg
https://farm4.staticflickr.com/3040/13086071753_265103ac38_n.jpg
https://farm8.staticflickr.com/7451/13086343854_a6858f84d2_n.jpg