如何使用Python etree lxml xpath设置/替换xml中的值？

我想用Python2.7和etree/lxml/xpath解析一个AndroidManifest.xml，以查找属性名，并获取和设置它们的值

AndroidManifest.xml：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.android.wearable.timer" >
<uses-sdk android:minSdkVersion="20"
          android:targetSdkVersion="22" />
<application
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.DeviceDefault.Light"
        android:allowBackup="true">
</application>
</manifest>

这就是我到目前为止所做的：

from lxml import etree
NS = {'android' : 'http://schemas.android.com/apk/res/android'}
tree = etree.parse('AndroidManifest.xml')
# get values
print tree.xpath("///@android:allowBackup", namespaces=NS)[0]
print tree.xpath("///@android:minSdkVersion", namespaces=NS)[0]
# set values ?
# write changes back to file ?
print etree.tostring(tree, encoding='utf-8', pretty_print=True)

这将打印true、20，然后打印整个未更改的xml文档

• 如何将allowBackup和minSdkVersion的值分别设置为false和19？

奖金：

• 如果android:allowBackup或android:minSdkVersion尚未出现，如何添加它们
• 如何将更改写回文件

这给了你：

<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.android.wearable.timer">
<uses-sdk android:minSdkVersion="17" android:targetSdkVersion="22"/>
<application android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:theme="@android:style/Theme.DeviceDefault.Light" android:allowBackup="false">
</application>
</manifest>

new.xml：

<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.android.wearable.timer">
<uses-sdk android:minSdkVersion="17" android:targetSdkVersion="22"/>
<application android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:theme="@android:style/Theme.DeviceDefault.Light" android:allowBackup="false">
</application>
</manifest>

您现在知道如何编写更改，对于丢失的属性，它将按原样工作，如果值存在，我们将更新它，如果不存在，我们将创建它：

# no minSDk...
In [31]: !cat  test.xml<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.android.wearable.timer" >
<uses-sdk  android:targetSdkVersion="22" />
<application
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.DeviceDefault.Light"
        android:allowBackup="true">
</application>
</manifest>
In [32]: tree = et.parse("test.xml")

In [33]: root = tree.getroot()

In [34]: nsmap = root.nsmap

In [35]: android = nsmap["android"]

In [36]: tree.find("uses-sdk", nsmap).attrib[et.QName(android, "minSdkVersion")] = "17"

In [37]: tree.write("test.xml", encoding="utf-8")

# New attribute and value created.
In [38]: !cat  test.xml<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.android.wearable.timer">
<uses-sdk android:targetSdkVersion="22" android:minSdkVersion="17"/>
<application android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:theme="@android:style/Theme.DeviceDefault.Light" android:allowBackup="true">
</application>
</manifest>
In [39]: 

#没有minSDk。。。
在[31]：！cat test.xml
在[32]中：tree=et.parse（“test.xml”）
在[33]中：root=tree.getroot（）
在[34]中：nsmap=root.nsmap
在[35]：android=nsmap[“android”]
在[36]中：tree.find（“使用sdk”，nsmap）.attrib[et.QName（android，“minSdkVersion”）]=“17”
[37]：tree.write（“test.xml”，encoding=“utf-8”）
#创建新属性和值。
在[38]：！cat test.xml
在[39]中：

<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.android.wearable.timer">
<uses-sdk android:minSdkVersion="17" android:targetSdkVersion="22"/>
<application android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:theme="@android:style/Theme.DeviceDefault.Light" android:allowBackup="false">
</application>
</manifest>

import lxml.etree as et
from StringIO import StringIO

tree = et.parse(StringIO(xml))
root = tree.getroot()
nsmap = root.nsmap
android = nsmap["android"]

tree.find("application", nsmap).attrib[et.QName(android, "allowBackup")] = "false"
tree.find("uses-sdk", nsmap).attrib[et.QName(android, "minSdkVersion")] = "17"

# write the updated html to "new.xml"
tree.write("new.xml", encoding="utf-8")

<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.android.wearable.timer">
<uses-sdk android:minSdkVersion="17" android:targetSdkVersion="22"/>
<application android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:theme="@android:style/Theme.DeviceDefault.Light" android:allowBackup="false">
</application>
</manifest>

# no minSDk...
In [31]: !cat  test.xml<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.android.wearable.timer" >
<uses-sdk  android:targetSdkVersion="22" />
<application
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.DeviceDefault.Light"
        android:allowBackup="true">
</application>
</manifest>
In [32]: tree = et.parse("test.xml")

In [33]: root = tree.getroot()

In [34]: nsmap = root.nsmap

In [35]: android = nsmap["android"]

In [36]: tree.find("uses-sdk", nsmap).attrib[et.QName(android, "minSdkVersion")] = "17"

In [37]: tree.write("test.xml", encoding="utf-8")

# New attribute and value created.
In [38]: !cat  test.xml<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.android.wearable.timer">
<uses-sdk android:targetSdkVersion="22" android:minSdkVersion="17"/>
<application android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:theme="@android:style/Theme.DeviceDefault.Light" android:allowBackup="true">
</application>
</manifest>
In [39]: