使用Python從XML文檔獲取多個子值

Question

我正在使用Python讀取XML METAR（Weather）數據。我可以讀取數據，並且還添加了錯誤檢查（僅適用於下面的visibility_statute_mi！）。下面是XML數據的例子：

<METAR> 
    <raw_text> 
    FALE 201800Z VRB01KT 9999 FEW016 BKN028 23/22 Q1010 NOSIG 
    </raw_text> 
    <station_id>FALE</station_id> 
    <observation_time>2013-01-20T18:00:00Z</observation_time> 
    <temp_c>23.0</temp_c> 
    <dewpoint_c>22.0</dewpoint_c> 
    <wind_dir_degrees>0</wind_dir_degrees> 
    <wind_speed_kt>1</wind_speed_kt> 
    <altim_in_hg>29.822834</altim_in_hg> 
    <quality_control_flags> 
    <no_signal>TRUE</no_signal> 
    </quality_control_flags> 
    <sky_condition sky_cover="FEW" cloud_base_ft_agl="1600"/> 
    <sky_condition sky_cover="BKN" cloud_base_ft_agl="2800"/> 
    <flight_category>MVFR</flight_category> 
    <metar_type>METAR</metar_type> 
</METAR> 

這裏是我的Python 2.7的代碼分析數據：

# Output the XML in a HTML friendly manner 
def outputHTML(xml): 
    # The get the METAR Data list 
    metar_data = xml.getElementsByTagName("data") 

    # Our return string 
    outputString = "" 

    # Cycled through the metar_data 
    for state in metar_data: 

     #Gets the stations and cycle through them 
     stations = state.getElementsByTagName("METAR") 
     for station in stations: 
      # Grab data from the station element 
      raw_text    = station.getElementsByTagName("raw_text")[0].firstChild.data 
      station_id    = station.getElementsByTagName("station_id")[0].firstChild.data 
      observation_time  = station.getElementsByTagName('observation_time')[0].firstChild.data 
      temp_c     = station.getElementsByTagName('temp_c')[0].firstChild.data 
      dewpoint_c    = station.getElementsByTagName('dewpoint_c')[0].firstChild.data 
      wind_dir_degrees  = station.getElementsByTagName('wind_dir_degrees')[0].firstChild.data 
      wind_speed_kt   = station.getElementsByTagName('wind_speed_kt')[0].firstChild.data 
      visibility_statute_mi = station.getElementsByTagName('visibility_statute_mi') 
      if len(visibility_statute_mi) > 0: 
       visibility_statute_mi = visibility_statute_mi[0].firstChild.data 
      altim_in_hg    = station.getElementsByTagName('altim_in_hg')[0].firstChild.data 
      metar_type    = station.getElementsByTagName('metar_type')[0].firstChild.data 

      # Append the data onto the string 
      string = "<tr><td>" + str(station_id) + "</td><td>" + str(observation_time) + "</td><td>" + str(raw_text) + "</td><td>" + str(temp_c) + "</td><td>" + str(dewpoint_c) + "</td></tr>" 
      outputString+=string 

    # Output string 
    return outputString  

如何閱讀sky_condition數據和循環得到sky_cover和cloud_base_ft_agl值？

我還需要檢查是否有任何天空狀況值，因爲通常沒有云層覆蓋，也沒有數據。

Andre

Answer 1

我會解析xml到樹中並查詢它，像這樣：

import xml.etree.ElementTree as et 

xmltext = """ 
<METAR> 
    <raw_text> 
    FALE 201800Z VRB01KT 9999 FEW016 BKN028 23/22 Q1010 NOSIG 
    </raw_text> 
    <station_id>FALE</station_id> 
    <observation_time>2013-01-20T18:00:00Z</observation_time> 
    <temp_c>23.0</temp_c> 
    <dewpoint_c>22.0</dewpoint_c> 
    <wind_dir_degrees>0</wind_dir_degrees> 
    <wind_speed_kt>1</wind_speed_kt> 
    <altim_in_hg>29.822834</altim_in_hg> 
    <quality_control_flags> 
    <no_signal>TRUE</no_signal> 
    </quality_control_flags> 
    <sky_condition sky_cover="FEW" cloud_base_ft_agl="1600"/> 
    <sky_condition sky_cover="BKN" cloud_base_ft_agl="2800"/> 
    <flight_category>MVFR</flight_category> 
    <metar_type>METAR</metar_type> 
</METAR> 
""" 
tree = et.fromstring(xmltext) 

for sky_con in tree.iterfind('sky_condition'): 
    print sky_con.attrib["cloud_base_ft_agl"] 
    print sky_con.attrib.keys() 

通過閱讀keys()你可以檢查你感興趣的屬性的存在

編輯：如果你想使用xml.dom.minidom你可以將這些行添加到您的站回覆提取相同的屬性：

for sky_con in station.getElementsByTagName("sky_condition"): 
    print sky_con._attrs["cloud_base_ft_agl"].value 
    print sky_con._attrs["sky_cover"].value