如何使用 Python ElementTree 在 XML 解析期间检查条件

debugcn 发表于 Dev

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我正在尝试使用 ElementTree 解析 XML 并获取所有必需的字段。

问题：我的列表变空了，我尝试的条件是 - 如果 reference('type') == 'cve' 那么我想在参考标签中获取 'id' 文本。

有人可以建议/纠正我获得必填字段吗？

我的实际代码如下：

import xml.etree.ElementTree as ET

file_name = "updateinfo.xml"
parser = ET.XMLParser(encoding="utf-8")
tree = ET.parse(file_name, parser=parser)
tree_toString = (ET.tostring(tree.getroot()))
for ele in tree.findall('update'):
    cveList = [
        ele.find('references/reference').get('id') if ele.find('references/reference').get('type') == 'cve' else None
        for cve in ele.find('references/reference')]
    print cveList

我的 XML 结构如下：

<?xml version="1.0" encoding="UTF-8"?>
<updates>
        <update status="final" from="[email protected]" version="4" type="enhancement" >
            <id>RHEA-2017:2259</id>
            <issued date="2017-08-01 05:59:34 UTC" />
            <title>new packages: usbguard</title>
            <release>0</release>
            <rights>Copyright 2017 Red Hat Inc</rights>
            <pushcount>4</pushcount>
            <updated date="2017-08-01 05:59:34 UTC" />
            <references>
                <reference href="https://access.redhat.com/errata/RHEA-2017:2259" type="self" id="RHEA-2017:2259" title="RHEA-2017:2259" />
                <reference href="https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/7.4_Release_Notes/index.html" type="other" id="ref_0" title="other_reference_0" />
            </references>
            <pkglist>
                <collection short="" >
                    <name>rhel-7-server-rpms__7_DOT_4__x86_64</name>
                    <package src="usbguard-0.7.0-3.el7.src.rpm" name="usbguard" epoch="0" version="0.7.0" release="3.el7" arch="i686" >
                        <filename>usbguard-0.7.0-3.el7.i686.rpm</filename>
                        <sum type="sha256" >efd5ca6dd3df02e8537cf45cef48508bf023f568a98ce9f28e9baf77c5caac6c</sum>
                    </package>
                    <package src="usbguard-0.7.0-3.el7.src.rpm" name="usbguard" epoch="0" version="0.7.0" release="3.el7" arch="x86_64" >
                        <filename>usbguard-0.7.0-3.el7.x86_64.rpm</filename>
                        <sum type="sha256" >3f72768880085d6bfff37636d3a8eb54184e5619353b5efbefd5738e74bdfa08</sum>
                    </package>
                </collection>
            </pkglist>
        </update>
        <update status="final" from="[email protected]" version="1" type="bugfix" >
            <id>RHBA-2014:0722</id>
            <issued date="2014-06-10 00:00:00" />
            <title>kexec-tools bug fix update</title>
            <rights>Copyright 2014 Red Hat Inc</rights>
            <pushcount>1</pushcount>
            <updated date="2014-06-10 00:00:00" />
            <references>
                <reference href="https://rhn.redhat.com/errata/RHBA-2014-0722.html" type="self" title="RHBA-2014:0722" />
            </references>
            <pkglist>
                <collection short="" >
                    <name>rhel-7-server-rpms__7_DOT_4__x86_64</name>
                    <package src="kexec-tools-2.0.4-32.el7_0.1.src.rpm" name="kexec-tools" epoch="0" version="2.0.4" release="32.el7_0.1" arch="x86_64" >
                        <filename>kexec-tools-2.0.4-32.el7_0.1.x86_64.rpm</filename>
                        <sum type="sha256" >8e214681104e4ba73726e0ce11d21b963ec0390fd70458d439ddc72372082034</sum>
                    </package>
                </collection>
            </pkglist>
        </update>
        <update status="final" from="[email protected]" version="4" type="security" >
            <id>RHSA-2017:2831</id>
            <issued date="2017-09-28 18:56:55 UTC" />
            <title>Critical: firefox security update</title>
            <release>0</release>
            <rights>Copyright 2017 Red Hat Inc</rights>
            <severity>Critical</severity>
            <pushcount>4</pushcount>
            <updated date="2017-09-28 18:56:56 UTC" />
            <references>
                <reference href="https://access.redhat.com/errata/RHSA-2017:2831" type="self" id="RHSA-2017:2831" title="RHSA-2017:2831" />
                <reference href="https://bugzilla.redhat.com/show_bug.cgi?id=1496649" type="bugzilla" id="1496649" title="CVE-2017-7793 Mozilla: Use-after-free with Fetch API (MFSA 2017-22)" />
                <reference href="https://bugzilla.redhat.com/show_bug.cgi?id=1496651" type="bugzilla" id="1496651" title="CVE-2017-7810 Mozilla: Memory safety bugs fixed in Firefox 56 and Firefox ESR 52.4 (MFSA 2017-22)" />
                <reference href="https://bugzilla.redhat.com/show_bug.cgi?id=1496652" type="bugzilla" id="1496652" title="CVE-2017-7814 Mozilla: Blob and data URLs bypass phishing and malware protection warnings (MFSA 2017-22)" />
                <reference href="https://bugzilla.redhat.com/show_bug.cgi?id=1496653" type="bugzilla" id="1496653" title="CVE-2017-7818 Mozilla: Use-after-free during ARIA array manipulation (MFSA 2017-22)" />
                <reference href="https://bugzilla.redhat.com/show_bug.cgi?id=1496654" type="bugzilla" id="1496654" title="CVE-2017-7819 Mozilla: Use-after-free while resizing images in design mode (MFSA 2017-22)" />
                <reference href="https://bugzilla.redhat.com/show_bug.cgi?id=1496655" type="bugzilla" id="1496655" title="CVE-2017-7823 Mozilla: CSP sandbox directive did not create a unique origin (MFSA 2017-22)" />
                <reference href="https://bugzilla.redhat.com/show_bug.cgi?id=1496656" type="bugzilla" id="1496656" title="CVE-2017-7824 Mozilla: Buffer overflow when drawing and validating elements with ANGLE (MFSA 2017-22)" />
                <reference href="https://www.redhat.com/security/data/cve/CVE-2017-7793.html" type="cve" id="CVE-2017-7793" title="CVE-2017-7793" />
                <reference href="https://www.redhat.com/security/data/cve/CVE-2017-7810.html" type="cve" id="CVE-2017-7810" title="CVE-2017-7810" />
                <reference href="https://www.redhat.com/security/data/cve/CVE-2017-7814.html" type="cve" id="CVE-2017-7814" title="CVE-2017-7814" />
                <reference href="https://www.redhat.com/security/data/cve/CVE-2017-7818.html" type="cve" id="CVE-2017-7818" title="CVE-2017-7818" />
                <reference href="https://www.redhat.com/security/data/cve/CVE-2017-7819.html" type="cve" id="CVE-2017-7819" title="CVE-2017-7819" />
                <reference href="https://www.redhat.com/security/data/cve/CVE-2017-7823.html" type="cve" id="CVE-2017-7823" title="CVE-2017-7823" />
                <reference href="https://www.redhat.com/security/data/cve/CVE-2017-7824.html" type="cve" id="CVE-2017-7824" title="CVE-2017-7824" />
                <reference href="https://access.redhat.com/security/updates/classification/#critical" type="other" id="classification" title="critical" />
                <reference href="https://www.mozilla.org/en-US/security/advisories/mfsa2017-22/" type="other" id="ref_0" title="other_reference_0" />
            </references>
            <pkglist>
                <collection short="" >
                    <name>rhel-7-server-rpms__7_DOT_4__x86_64</name>
                    <package src="firefox-52.4.0-1.el7_4.src.rpm" name="firefox" epoch="0" version="52.4.0" release="1.el7_4" arch="x86_64" >
                        <filename>firefox-52.4.0-1.el7_4.x86_64.rpm</filename>
                        <sum type="sha256" >7b81b37bf969534bee0152bc13db56ae410eee06120a78d8da261c10c73c0514</sum>
                    </package>
                </collection>
            </pkglist>
        </update>
        <update status="final" from="[email protected]" version="2" type="bugfix" >
            <id>RHBA-2016:2423</id>
            <issued date="2016-11-03 06:09:21 UTC" />
            <title>oscap-anaconda-addon bug fix update</title>
            <release>0</release>
            <rights>Copyright 2016 Red Hat Inc</rights>
            <severity>None</severity>
            <pushcount>2</pushcount>
            <updated date="2016-11-03 06:10:44 UTC" />
            <references>
                <reference href="https://access.redhat.com/errata/RHBA-2016:2423" type="self" id="RHBA-2016:2423" title="RHBA-2016:2423" />
                <reference href="https://bugzilla.redhat.com/show_bug.cgi?id=1269211" type="bugzilla" id="1269211" title="could move security section down to bottom since it's not as important as network spoke" />
            </references>
            <pkglist>
                <collection short="" >
                    <name>rhel-7-server-rpms__7_DOT_4__x86_64</name>
                    <package src="oscap-anaconda-addon-0.7-12.el7.src.rpm" name="oscap-anaconda-addon" epoch="0" version="0.7" release="12.el7" arch="noarch" >
                        <filename>oscap-anaconda-addon-0.7-12.el7.noarch.rpm</filename>
                        <sum type="sha256" >507fbf46ddaed0bb4087d3ef2b31db235473f3be36aaa9ed7df43279ed7e2f07</sum>
                    </package>
                </collection>
            </pkglist>
        </update>

stovfl

问题：如何在 XML 解析过程中检查条件

你在做什么，不是解析，因为这一行已经完成了解析：
tree = ET.parse(file_name, parser=parser)
你不需要通过parser=XMLParser，因为这是标准的解析器。
阅读参考：xml.etree.ElementTree.parse

您的示例代码循环了ElementTree 四次。
for ele in tree.findall('update'):
    cveList = [
        ele.find('references/reference').get('id') if ele.find('references/reference').get('type') == 'cve' else None
        for cve in ele.find('references/reference')]
Every .find..., 将循环直到找到请求的元素或直到结束。
你应该避免这样的嵌套编码！

您可以reference通过一个循环获取所有元素，例如：

import xml.etree.ElementTree as ET

file_name = "test/updateinfo.xml"
tree = ET.parse(file_name)

cveList = []
for reference in tree.findall('update/references/reference'):
    if reference.attrib.get('type') == 'cve':
        cveList.append(reference.attrib.get('id'))

print(cveList)

输出：

['CVE-2017-7793', 'CVE-2017-7810', 'CVE-2017-7814', 'CVE-2017-7818', 'CVE-2017-7819', 'CVE-2017-7823', 'CVE-2017-7824']

评论：每个更新项的 cveList，而不是获取一个列表中的所有项。我想在每次更新中迭代并获取其他属性

# Findall 'update' Elements in tree
for update in tree.findall('update'):
    # Findall 'references/reference' in update
    for reference in update.findall('references/reference'):
        if reference.attrib.get('type') == 'cve':
            # Find Element with tag <title> in update
            title = update.find('title').text
            # Append a Dict with keys 'title' and 'id'
            cveList.append({'title': title, 'id': reference.get('id')})

输出：

[{'id': 'CVE-2017-7793', 'title': 'Critical: firefox security update'}, {'id': 'CVE-2017-7810', 'title': 'Critical: firefox security update'}, {'id': 'CVE-2017-7814', 'title': 'Critical: firefox security update'}, {'id': 'CVE-2017-7818', 'title': 'Critical: firefox security update'}, {'id': 'CVE-2017-7819', 'title': 'Critical: firefox security update'}, {'id': 'CVE-2017-7823', 'title': 'Critical: firefox security update'}, {'id': 'CVE-2017-7824', 'title': 'Critical: firefox security update'}]

用 Python 测试：2.7.9

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