无法分析XML响应并获取元素

Question

这是我对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>

我尝试使用python3.5解析这个XML内容

^{pr2}$

当我打印这个时，我得到一个None。我做错什么了？我还想访问“Array”标记，但它也返回None。在

Answer 1

如the doc所述，由于数据集根标记的xmlns="http://xml.opendap.org/ns/DAP2"属性，您要查找的所有标记名都必须以{http://xml.opendap.org/ns/DAP2}作为前缀。在

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

阅读ElementTree文档的这一部分还将向您展示如何使用名称空间的词法使内容更具可读性。在

Answer 2

XML文档使用名称空间，因此您需要在代码中支持它。在^{} documentation中有一个解释和示例代码。在

基本上可以这样做：

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>