无法解析XML响应并获取元素

Question

这是来自http请求的XML响应。

<?xml version="1.0" encoding="UTF-8"?>
<Dataset name="aggregations/g/ds083.2/2/TP"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://xml.opendap.org/ns/DAP2"
 xsi:schemaLocation="http://xml.opendap.org/ns/DAP2          
http://xml.opendap.org/dap/dap2.xsd" >

    <Attribute name="NC_GLOBAL" type="Container">
        <Attribute name="Originating_or_generating_Center" type="String">
            <value>US National Weather Service, National Centres for Environmental Prediction (NCEP)</value>
        </Attribute>
        <Attribute name="Originating_or_generating_Subcenter" type="String">
            <value>0</value>
        </Attribute>
        <Attribute name="GRIB_table_version" type="String">
            <value>2,1</value>
        </Attribute>
        <Attribute name="Type_of_generating_process" type="String">
            <value>Forecast</value>
        </Attribute>
        <Attribute name="Analysis_or_forecast_generating_process_identifier_defined_by_originating_centre" type="String">
            <value>Analysis from GDAS (Global Data Assimilation System)</value>
        </Attribute>
        <Attribute name="file_format" type="String">
            <value>GRIB-2</value>
        </Attribute>
        <Attribute name="Conventions" type="String">
            <value>CF-1.6</value>
        </Attribute>
        <Attribute name="history" type="String">
            <value>Read using CDM IOSP GribCollection v3</value>
        </Attribute>
        <Attribute name="featureType" type="String">
            <value>GRID</value>
        </Attribute>
        <Attribute name="_CoordSysBuilder" type="String">
            <value>ucar.nc2.dataset.conv.CF1Convention</value>
        </Attribute>
    </Attribute>

    <Array name="time1">
        <Attribute name="units" type="String">
            <value>Hour since 2007-12-06T12:00:00Z</value>
        </Attribute>
        <Attribute name="standard_name" type="String">
            <value>time</value>
        </Attribute>
        <Attribute name="long_name" type="String">
            <value>GRIB forecast or observation time</value>
        </Attribute>
        <Attribute name="calendar" type="String">
            <value>proleptic_gregorian</value>
        </Attribute>
        <Attribute name="_CoordinateAxisType" type="String">
            <value>Time</value>
        </Attribute>
        <Float64/>
        <dimension name="time1" size="10380"/>
    </Array>

</Dataset>

我正在尝试使用Python3.5解析这个XML内容

from xml.etree import ElementTree

response = requests.get("http://rda.ucar.edu/thredds/dodsC/aggregations/g/ds083.2/2/TP.ddx?time1")

tree = ElementTree.fromstring(response.content)

attr = tree.find("Attribute")
print(attr)

当我打印这个时，我会得到一个None。我做错了什么？我还想访问"Array“标记，但这也会返回None。

Answer 1

XML文档使用名称空间，因此您需要在代码中支持这一点。在文档中有一个解释和示例代码。

基本上你可以这样做：

import requests
from xml.etree import ElementTree

response = requests.get('http://rda.ucar.edu/thredds/dodsC/aggregations/g/ds083.2/2/TP.ddx?time1')

tree = ElementTree.fromstring(response.content)

attr = tree.find("{http://xml.opendap.org/ns/DAP2}Attribute")

>>> print(attr)
<Element '{http://xml.opendap.org/ns/DAP2}Attribute' at 0x7f147a292458>

# or declare the namespace like this
ns = {'dap2': 'http://xml.opendap.org/ns/DAP2'}
attr = tree.find("dap2:Attribute", ns)

>>> print(attr)
<Element '{http://xml.opendap.org/ns/DAP2}Attribute' at 0x7f147a292458>

Answer 2

正如医生中所述，由于Dataset根标记的xmlns="http://xml.opendap.org/ns/DAP2"属性，您要查找的所有标记名称都必须以{http://xml.opendap.org/ns/DAP2}作为前缀。

# should find something
tree.find("{http://xml.opendap.org/ns/DAP2}Attribute")

阅读ElementTree文档的这一节还将向您展示如何使用名称空间字典来提高某些内容的可读性。