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我试图从一个长的 xml 文档中获取一些属性。具体来说，我希望获得该代码可靠地完成的阶段 cfs 和 ft 级别。困难是我似乎无法弄清楚如何从标签中提取时间戳作为日期时间值，类似于：

<ns1:value qualifiers="P" dateTime="2012-11-01T18:45:00.000-05:00">54800</ns1:value>

非常感谢任何帮助和改进建议。

def getLevels(gaugeId):

    # create url string 00060=cfs and 00065=ft
    urlRoot = "http://waterservices.usgs.gov/nwis/iv/?format=waterml,1.1&sites="
    urlTail = "&parameterCd=00060,00065"
    url = urlRoot + str(gaugeId) + urlTail
    del urlRoot, urlTail

    # open connection to url
    urlFile = urllib2.urlopen(url)

    # convert urlFile to string data:
    urlData = urlFile.read()

    # close file to release memory
    urlFile.close()

    # parse downloaded xml
    domData = parseString(urlData)

    # extract xml element values for stage cfs and ft
    index = 0
    elementCount = domData.getElementsByTagName("ns1:value").length
    output = []
    while elementCount >= index:
        xmlString = domData.getElementsByTagName("ns1:value")[index].toxml()
        output.append(stripXmlTags(xmlString))
        index = index + 1

    # extract and return
    return output
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2 回答 2

0

ElementTree 的 iter() 方法也可以方便地获取一些您想要的数据，如下所示。一些示例输出跟随程序。

#!/usr/bin/env python
from xml.etree import cElementTree as ET
from datetime import datetime
import re

with open('waterservices.usgs.gov.xml','r') as fi:
    waterData = ''.join(fi.readlines())
waterData = re.sub('ns[12]:', '', waterData)
root = ET.fromstring(waterData)
dates = [v.get('dateTime') for v in root.iter('value')]
valus = [float(v.text) for v in root.iter('value')]
units = [v.text for v in root.iter('variableName')]
print 'valus', valus
print 'units', units
print 'dates', dates
dates = [datetime.strptime(t[:-6], '%Y-%m-%dT%H:%M:%S.%f') for t in dates]
print 'dates', dates
a = zip (valus, units, dates)
for v in a:
    print v

（注意，我不知道如何正确处理前缀ns1:和，ns2:因此在上面通过re.sub. urllib2，不处理时区。）下面的示例输出基于 来自问题链接的XML 数据文件，保存为本地文件waterservices.usgs.gov.xml。 

valus [53200.0, 6.86]
units ['Streamflow, ft&#179;/s', 'Gage height, ft']
dates ['2012-11-01T19:45:00.000-05:00', '2012-11-01T19:45:00.000-05:00']
dates [datetime.datetime(2012, 11, 1, 19, 45), datetime.datetime(2012, 11, 1, 19, 45)]
(53200.0, 'Streamflow, ft&#179;/s', datetime.datetime(2012, 11, 1, 19, 45))
(6.86, 'Gage height, ft', datetime.datetime(2012, 11, 1, 19, 45))
于 2012-11-02T08:15:42.153 回答
0

您可以以此为起点 - 请注意，这目前忽略了时区...

from xml.etree import ElementTree as ET

tree = ET.fromstring(urlData)
for elem in tree.findall('.//{http://www.cuahsi.org/waterML/1.1/}value'):
    print datetime.strptime(elem.attrib['dateTime'][:-10], '%Y-%m-%dT%H:%M:%S')
于 2012-11-02T01:35:31.067 回答