Python XML提取循环

Question

我有一段脚本，感觉快完成了。我找到了一个简单的方法来写它，但我不知道怎么把它变成一个循环。

我正在从一个xml文件中提取数据，这个文件的格式是这样的：

<Trackpoint>
    <Time>2012-01-17T11:44:35Z</Time>
    <Position>
        <LatitudeDegrees>51.920211518183351</LatitudeDegrees>
        <LongitudeDegrees>26.706042898818851</LongitudeDegrees>
    </Position>
    <AltitudeMeters>-43.6026611328125</AltitudeMeters>
</Trackpoint>
<Trackpoint>
    <Time>2012-01-17T11:45:21Z</Time>
    <Position>
        <LatitudeDegrees>51.920243117958307</LatitudeDegrees>
        <LongitudeDegrees>26.706140967085958</LongitudeDegrees>
    </Position>
    <AltitudeMeters>-43.6026611328125</AltitudeMeters>
</Trackpoint>

我可以用下面的代码来获取，比如说纬度：

from xml.dom.minidom import parse
doc = parse('/Users/name/Documents/GPS/gps.tcx')
lat = doc.getElementsByTagName("LatitudeDegrees")
time = doc.getElementsByTagName("Time")
trackpoint = doc.getElementsByTagName("Trackpoint")

for x in lat:
    print(x.firstChild.data)

但是我想要按顺序获取纬度、经度和时间。

我猜我需要使用

for x in trackpoint 

但我目前想到的实现方式是这样的。

count = 0
n = len(trackpoint)
while count < n:
    print(time[count].firstChild.data)
    print(lat[count].firstChild.data)
    print(lon[count].firstChild.data)
    count += 1

有没有人有什么想法？我觉得我只是缺少了一些很简单的东西！

Answer 1

也许你在寻找zip这个功能:

import xml.dom.minidom as minidom
import os

doc = minidom.parse(os.path.expanduser('~/test/gps.tcx'))
latitudes = doc.getElementsByTagName("LatitudeDegrees")
longitudes = doc.getElementsByTagName("LongitudeDegrees")
time = doc.getElementsByTagName("Time")
trackpoint = doc.getElementsByTagName("Trackpoint")

for t,lat,lon in zip(time,latitudes,longitudes):
    print(t.firstChild.data, lat.firstChild.data, lon.firstChild.data)

Answer 2

我通常觉得用 ElementTree 来解析 XML 文件更容易理解，也更简单。例如，你可以用三行代码读取纬度。

import xml.etree.ElementTree as etree

s="""<root>
<Trackpoint>
    <Time>2012-01-17T11:44:35Z</Time>
    <Position>
        <LatitudeDegrees>51.920211518183351</LatitudeDegrees>
        <LongitudeDegrees>26.706042898818851</LongitudeDegrees>
    </Position>
    <AltitudeMeters>-43.6026611328125</AltitudeMeters>
</Trackpoint>
<Trackpoint>
    <Time>2012-01-17T11:45:21Z</Time>
    <Position>
        <LatitudeDegrees>51.920243117958307</LatitudeDegrees>
        <LongitudeDegrees>26.706140967085958</LongitudeDegrees>
    </Position>
    <AltitudeMeters>-43.6026611328125</AltitudeMeters>
</Trackpoint>
</root>
"""

root = etree.fromstring(s)
for point in root:
    print point.find('Position/LatitudeDegrees').text

假设你想把每个点转换成一个字典。

varnames = [
    ('Position/LatitudeDegrees', 'lat'),
    ('Position/LongitudeDegrees', 'lon'),
    ('Time', 'time'),
    ('AltitudeMeters', 'alt')
    ]

points = []
for pointelem in etree.fromstring(s):
    point = {}
    for tag, varname in varnames:
        point[varname] = pointelem.find(tag).text
    points.append(point)

import pprint
pprint.pprint(points)

输出结果：

[{'alt': '-43.6026611328125',
  'lat': '51.920211518183351',
  'lon': '26.706042898818851',
  'time': '2012-01-17T11:44:35Z'},
 {'alt': '-43.6026611328125',
  'lat': '51.920243117958307',
  'lon': '26.706140967085958',
  'time': '2012-01-17T11:45:21Z'}]

Answer 3

首先，找到所有的 Trackpoint 元素，然后对它们进行循环。接着，在循环中找到每个 Trackpoint 元素想要的子元素：

from xml.dom.minidom import parse

doc = parse('in.tcx')

trackpoints = doc.getElementsByTagName("Trackpoint")
result = []
elements = ('Time', 'LatitudeDegrees', 'LongitudeDegrees')
for tp in trackpoints:
    obj = {}
    for el in elements:
        obj[el] = tp.getElementsByTagName(el)[0].firstChild.data
    result.append(obj)


print(result)