我多年来一直在抨击我，我一定是在做一些愚蠢的事。
我正在尝试检索所有可能的维基百科支持的语言，并通过遍历List_of_Wikipedias上的表格将它们输出到文本文件。
到目前为止，这是我的python代码，它只是试图检索其中一个表：
import httplib
from lxml import etree
def main():
conn = httplib.HTTPConnection("meta.wikimedia.org")
conn.request("GET","/wiki/List_of_Wikipedias")
res = conn.getresponse()
root = etree.fromstring(res.read())
table = root.xpath('//table')
print table
main()
在我的机器上，这只打印一个空列表。为了提高速度，我在本地缓存了页面并使用了：
wikipage = open("wikipage.html")
root = lxml.parse(wikipage)
但这不会产生任何影响（除了显而易见的加速）。我也试过
lxml.find('table')
和
for element in root.iter():
print("%s - %s" % (element.tag, element.text))
成功打印出所有元素，因此我知道正在创建树。
我做错了什么？
任何帮助将不胜感激。 感谢。
答案 0 :(得分：3)
I am trying to retrieve all of the possible Wikipedia supported languages and output them to a text file by traversing the tables on List_of_Wikipedias
您的问题是文档中的元素名称位于默认命名空间中。如何编写涉及这些元素名称的XPath表达式是XPath中最常见的FAQ，并且在SO xpath标记中有很多好的答案。只是搜索它们。
这是一个完整的解决方案：
使用：
(//x:table)[1]/x:tr[not(x:th)]/x:td[2]//text()
您已注册绑定到前缀"http://www.w3.org/1999/xhtml"的XHTML名称空间（"x"）。
当我根据从http://s23.org/wikistats/wikipedias_html
获得的文档评估此XPath表达式时我需要在文档开头添加以下内容，因为我在本地工作并且没有XDML的DTD - 也许你不需要这些：
<!DOCTYPE html [
<!ENTITY uarr "↑">
<!ENTITY darr "↓">
<!ENTITY ccedil "Ç">
<!ENTITY oslash "Ø">
<!ENTITY aacute "á">
<!ENTITY aring "å">
<!ENTITY agrave "À">
<!ENTITY egrave "è">
<!ENTITY ograve "Ò">
<!ENTITY ocirc "ô">
]>
将上述XPath表达式应用于此文档的结果是：
English
German
French
Polish
Italian
Japanese
Spanish
Portuguese
Dutch
Russian
Swedish
Chinese
Catalan
Norwegian (Bokmål)
Finnish
Ukrainian
Czech
Hungarian
Romanian
Korean
Turkish
Vietnamese
Indonesian
Danish
Arabic
Esperanto
Serbian
Lithuanian
Slovak
Volapük
Persian
Hebrew
Bulgarian
Slovenian
Malay
Waray-Waray
Croatian
Estonian
Newar / Nepal Bhasa
Simple English
Hindi
Galician
Thai
Basque
Norwegian (Nynorsk)
Aromanian
Greek
Haitian
Azerbaijani
Tagalog
Latin
Telugu
Georgian
Macedonian
Cebuano
Serbo-Croatian
Breton
Piedmontese
Marathi
Latvian
Luxembourgish
Javanese
Belarusian (Taraškievica)
Welsh
Icelandic
Bosnian
Albanian
Tamil
Belarusian
Bishnupriya Manipuri
Aragonese
Occitan
Bengali
Swahili
Ido
Lombard
West Frisian
Gujarati
Afrikaans
Low Saxon
Malayalam
Quechua
Sicilian
Urdu
Kurdish
Cantonese
Sundanese
Asturian
Neapolitan
Samogitian
Armenian
Yoruba
Irish
Chuvash
Walloon
Nepali
Ripuarian
Western Panjabi
Kannada
Tajik
Tarantino
Venetian
Yiddish
Scottish Gaelic
Tatar
Min Nan
Ossetian
Uzbek
Alemannic
Kapampangan
Sakha
Egyptian Arabic
Kazakh
Maori
Limburgian
Amharic
Nahuatl
Upper Sorbian
Gilaki
Corsican
Gan
Mongolian
Scots
Interlingua
Central_Bicolano
Burmese
Faroese
Võro
Dutch Low Saxon
Sinhalese
Turkmen
West Flemish
Sanskrit
Bavarian
Malagasy
Manx
Ilokano
Divehi
Norman
Pangasinan
Banyumasan
Sorani
Romansh
Northern Sami
Zazaki
Mazandarani
Wu
Friulian
Uyghur
Ligurian
Maltese
Bihari
Novial
Tibetan
Anglo-Saxon
Kashubian
Sardinian
Classical Chinese
Fiji Hindi
Khmer
Ladino
Zamboanga Chavacano
Pali
Franco-Provençal/Arpitan
Pashto
Hakka
Cornish
Punjabi
Navajo
Silesian
Kalmyk
Pennsylvania German
Hawaiian
Saterland Frisian
Interlingue
Somali
Komi
Karachay-Balkar
Crimean Tatar
Tongan
Acehnese
Meadow Mari
Picard
Erzya
Lingala
Kinyarwanda
Extremaduran
Guarani
Kirghiz
Emilian-Romagnol
Assyrian Neo-Aramaic
Papiamentu
Aymara
Chechen
Lojban
Wolof
Banjar
Bashkir
North Frisian
Greenlandic
Tok Pisin
Udmurt
Kabyle
Tahitian
Sranan
Zealandic
Hill Mari
Komi-Permyak
Lower Sorbian
Abkhazian
Gagauz
Igbo
Oriya
Lao
Kongo
Avar
Moksha
Mirandese
Romani
Old Church Slavonic
Karakalpak
Samoan
Moldovan
Tetum
Gothic
Kashmiri
Bambara
Inupiak
Sindhi
Bislama
Lak
Nauruan
Norfolk
Inuktitut
Pontic
Assamese
Cherokee
Min Dong
Swati
Palatinate German
Hausa
Ewe
Tigrinya
Oromo
Zulu
Zhuang
Venda
Tsonga
Kirundi
Dzongkha
Sango
Cree
Chamorro
Luganda
Buginese
Buryat (Russia)
Fijian
Chichewa
Akan
Sesotho
Xhosa
Fula
Tswana
Kikuyu
Tumbuka
Shona
Twi
Cheyenne
Ndonga
Sichuan Yi
Choctaw
Marshallese
Afar
Kuanyama
Hiri Motu
Muscogee
Kanuri
Herero
请注意：每隔一个选定节点是仅限空格的文本节点。如果您不想选择这些，请使用：
(//x:table)[1]/x:tr[not(x:th)]/x:td[2]//text()[normalize-space()]
答案 1 :(得分：3)
将其解析为html。
from lxml import html
url = 'http://meta.wikimedia.org/wiki/List_of_Wikipedias'
tree = html.parse(url)
languages = tree.xpath('//table/tr/td[2]/a/text()')
print('\n'.join(languages))
English
German
French
Polish
Italian
Japanese
Spanish
Portuguese
Dutch
Russian
Swedish
Chinese
Catalan
Norwegian (Bokmål)
Finnish
Ukrainian
Czech
Hungarian
Romanian
Korean
Turkish
Vietnamese
Indonesian
Danish
Arabic
Esperanto
Serbian
Lithuanian
Slovak
Volapük
Persian
Hebrew
Bulgarian
Slovenian
Malay
Waray-Waray
Croatian
Estonian
Newar / Nepal Bhasa
Simple English
Hindi
Galician
Thai
Basque
Norwegian (Nynorsk)
Aromanian
Greek
Haitian
Azerbaijani
Tagalog
Latin
Telugu
Georgian
Macedonian
Cebuano
Serbo-Croatian
Breton
Piedmontese
Marathi
Latvian
Luxembourgish
Javanese
Belarusian (Taraškievica)
Welsh
Icelandic
Bosnian
Albanian
Tamil
Belarusian
Bishnupriya Manipuri
Aragonese
Occitan
Bengali
Swahili
Ido
Lombard
West Frisian
Gujarati
Afrikaans
Low Saxon
Malayalam
Quechua
Sicilian
Urdu
Kurdish
Cantonese
Sundanese
Asturian
Neapolitan
Samogitian
Armenian
Yoruba
Irish
Chuvash
Walloon
Nepali
Ripuarian
Western Panjabi
Kannada
Tajik
Tarantino
Venetian
Yiddish
Scottish Gaelic
Tatar
Min Nan
Ossetian
Uzbek
Alemannic
Kapampangan
Sakha
Kazakh
Egyptian Arabic
Maori
Amharic
Limburgian
Nahuatl
Upper Sorbian
Gilaki
Corsican
Gan
Mongolian
Scots
Interlingua
Central_Bicolano
Burmese
Faroese
Võro
Dutch Low Saxon
Sinhalese
Turkmen
West Flemish
Sanskrit
Bavarian
Malagasy
Manx
Ilokano
Divehi
Norman
Pangasinan
Banyumasan
Sorani
Romansh
Northern Sami
Zazaki
Mazandarani
Wu
Friulian
Uyghur
Ligurian
Maltese
Bihari
Novial
Tibetan
Anglo-Saxon
Kashubian
Sardinian
Classical Chinese
Fiji Hindi
Khmer
Ladino
Zamboanga Chavacano
Pali
Franco-Provençal/Arpitan
Pashto
Hakka
Cornish
Punjabi
Navajo
Silesian
Kalmyk
Pennsylvania German
Hawaiian
Saterland Frisian
Interlingue
Somali
Komi
Karachay-Balkar
Crimean Tatar
Tongan
Acehnese
Meadow Mari
Picard
Kinyarwanda
Erzya
Lingala
Extremaduran
Guarani
Kirghiz
Emilian-Romagnol
Assyrian Neo-Aramaic
Papiamentu
Aymara
Chechen
Lojban
Wolof
Banjar
Bashkir
North Frisian
Greenlandic
Tok Pisin
Udmurt
Kabyle
Tahitian
Sranan
Zealandic
Hill Mari
Komi-Permyak
Lower Sorbian
Abkhazian
Gagauz
Igbo
Oriya
Lao
Kongo
Avar
Moksha
Mirandese
Romani
Old Church Slavonic
Karakalpak
Samoan
Moldovan
Tetum
Gothic
Kashmiri
Bambara
Inupiak
Sindhi
Bislama
Lak
Nauruan
Norfolk
Inuktitut
Pontic
Assamese
Cherokee
Min Dong
Palatinate German
Swati
Hausa
Ewe
Tigrinya
Oromo
Zulu
Zhuang
Venda
Tsonga
Kirundi
Cree
Dzongkha
Sango
Chamorro
Luganda
Buginese
Buryat (Russia)
Fijian
Chichewa
Akan
Sesotho
Xhosa
Fula
Tswana
Kikuyu
Tumbuka
Shona
Twi
Cheyenne
Ndonga
Sichuan Yi
Choctaw
Marshallese
Afar
Kuanyama
Hiri Motu
Muscogee
Kanuri
Herero
答案 2 :(得分：0)
XPath需要名称空间。您下载的页面开始：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" dir="ltr">
所以你真的想要
xpath('//html:table')
其中html是绑定到"http://www.w3.org/1999/xhtml"
你必须找到如何在lxml中绑定名称空间 - 我不是python专家。
如果这是你的问题我同情 - 它已经把我和其他许多人赶了出来！