1、簡介html
XPath 是一門在 XML 文檔中查找信息的語言。XPath 可用來在 XML 文檔中對元素和屬性進行遍歷。XPath 是 W3C XSLT 標準的主要元素，而且 XQuery 和 XPointer 都構建於 XPath 表達之上。python
參照python爬蟲
2、安裝scrapy
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pip3 install lxml
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3、使用ide
一、導入post
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from
lxml
import
etree
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二、基本使用ui
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from
lxml
import
etree
wb_data
=
"""
<div>
<ul>
<li class="item-0"><a href="link1.html">first item</a></li>
<li class="item-1"><a href="link2.html">second item</a></li>
<li class="item-inactive"><a href="link3.html">third item</a></li>
<li class="item-1"><a href="link4.html">fourth item</a></li>
<li class="item-0"><a href="link5.html">fifth item</a>
</ul>
</div>
"""
html
=
etree.HTML(wb_data)
print
(html)
result
=
etree.tostring(html)
print
(result.decode(
"utf-8"
))
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從下面的結果來看，咱們打印機html其實就是一個python對象，etree.tostring(html)則是不全裏html的基本寫法，補全了缺胳膊少腿的標籤。url
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<Element html at
0x39e58f0
>
<html><body><div>
<ul>
<li
class
=
"item-0"
><a href
=
"link1.html"
>first item<
/
a><
/
li>
<li
class
=
"item-1"
><a href
=
"link2.html"
>second item<
/
a><
/
li>
<li
class
=
"item-inactive"
><a href
=
"link3.html"
>third item<
/
a><
/
li>
<li
class
=
"item-1"
><a href
=
"link4.html"
>fourth item<
/
a><
/
li>
<li
class
=
"item-0"
><a href
=
"link5.html"
>fifth item<
/
a>
<
/
li><
/
ul>
<
/
div>
<
/
body><
/
html>
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三、獲取某個標籤的內容(基本使用)，注意，獲取a標籤的全部內容，a後面就不用再加正斜槓，不然報錯。spa
寫法一code
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'/html/body/div/ul/li/a'
)
print
(html)
for
i
in
html_data:
print
(i.text)
<Element html at
0x12fe4b8
>
first item
second item
third item
fourth item
fifth item
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寫法二（直接在須要查找內容的標籤後面加一個/text()就行）
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'/html/body/div/ul/li/a/text()'
)
print
(html)
for
i
in
html_data:
print
(i)
<Element html at
0x138e4b8
>
first item
second item
third item
fourth item
fifth item
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四、打開讀取html文件
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#使用parse打開html的文件
html
=
etree.parse(
'test.html'
)
html_data
=
html.xpath(
'//*'
)<br>
#打印是一個列表，須要遍歷
print
(html_data)
for
i
in
html_data:
print
(i.text)
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html
=
etree.parse(
'test.html'
)
html_data
=
etree.tostring(html,pretty_print
=
True
)
res
=
html_data.decode(
'utf-8'
)
print
(res)
打印：
<div>
<ul>
<li
class
=
"item-0"
><a href
=
"link1.html"
>first item<
/
a><
/
li>
<li
class
=
"item-1"
><a href
=
"link2.html"
>second item<
/
a><
/
li>
<li
class
=
"item-inactive"
><a href
=
"link3.html"
>third item<
/
a><
/
li>
<li
class
=
"item-1"
><a href
=
"link4.html"
>fourth item<
/
a><
/
li>
<li
class
=
"item-0"
><a href
=
"link5.html"
>fifth item<
/
a><
/
li>
<
/
ul>
<
/
div>
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五、打印指定路徑下a標籤的屬性（能夠經過遍歷拿到某個屬性的值，查找標籤的內容）
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'/html/body/div/ul/li/a/@href'
)
for
i
in
html_data:
print
(i)
打印：
link1.html
link2.html
link3.html
link4.html
link5.html
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六、咱們知道咱們使用xpath拿到得都是一個個的ElementTree對象，因此若是須要查找內容的話，還須要遍歷拿到數據的列表。
查到絕對路徑下a標籤屬性等於link2.html的內容。
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'/html/body/div/ul/li/a[@href="link2.html"]/text()'
)
print
(html_data)
for
i
in
html_data:
print
(i)
打印：
[
'second item'
]
second item
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七、上面咱們找到所有都是絕對路徑（每個都是從根開始查找），下面咱們查找相對路徑，例如，查找全部li標籤下的a標籤內容。
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'//li/a/text()'
)
print
(html_data)
for
i
in
html_data:
print
(i)
打印：
[
'first item'
,
'second item'
,
'third item'
,
'fourth item'
,
'fifth item'
]
first item
second item
third item
fourth item
fifth item
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八、上面咱們使用絕對路徑，查找了全部a標籤的屬性等於href屬性值，利用的是/---絕對路徑，下面咱們使用相對路徑，查找一下l相對路徑下li標籤下的a標籤下的href屬性的值，注意，a標籤後面須要雙//。
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'//li/a//@href'
)
print
(html_data)
for
i
in
html_data:
print
(i)
打印：
[
'link1.html'
,
'link2.html'
,
'link3.html'
,
'link4.html'
,
'link5.html'
]
link1.html
link2.html
link3.html
link4.html
link5.html
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九、相對路徑下跟絕對路徑下查特定屬性的方法相似，也能夠說相同。
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'//li/a[@href="link2.html"]'
)
print
(html_data)
for
i
in
html_data:
print
(i.text)
打印：
[<Element a at
0x216e468
>]
second item
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十、查找最後一個li標籤裏的a標籤的href屬性
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'//li[last()]/a/text()'
)
print
(html_data)
for
i
in
html_data:
print
(i)
打印：
[
'fifth item'
]
fifth item
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十一、查找倒數第二個li標籤裏的a標籤的href屬性
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'//li[last()-1]/a/text()'
)
print
(html_data)
for
i
in
html_data:
print
(i)
打印：
[
'fourth item'
]
fourth item
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十二、若是在提取某個頁面的某個標籤的xpath路徑的話，能夠以下圖：
//*[@id="kw"]
解釋：使用相對路徑查找全部的標籤，屬性id等於kw的標籤。
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from scrapy.selector import Selector, HtmlXPathSelector
from scrapy.http import HtmlResponse
html = """<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
</head>
<body>
<ul>
<li class="item-"><a id='i1' href="link.html">first item</a></li>
<li class="item-0"><a id='i2' href="llink.html">first item</a></li>
<li class="item-1"><a href="llink2.html">second item<span>vv</span></a></li>
</ul>
<div><a href="llink2.html">second item</a></div>
</body>
</html>
"""
response = HtmlResponse(url='http://example.com', body=html,encoding='utf-8')
# hxs = HtmlXPathSelector(response)
# print(hxs)
# hxs = Selector(response=response).xpath('//a')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[2]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[@id]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[@id="i1"]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[@href="link.html"][@id="i1"]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[contains(@href, "link")]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[starts-with(@href, "link")]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[re:test(@id, "i\d+")]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[re:test(@id, "i\d+")]/text()').extract()
# print(hxs)
# hxs = Selector(response=response).xpath('//a[re:test(@id, "i\d+")]/@href').extract()
# print(hxs)
# hxs = Selector(response=response).xpath('/html/body/ul/li/a/@href').extract()
# print(hxs)
# hxs = Selector(response=response).xpath('//body/ul/li/a/@href').extract_first()
# print(hxs)
# ul_list = Selector(response=response).xpath('//body/ul/li')
# for item in ul_list:
# v = item.xpath('./a/span')
# # 或
# # v = item.xpath('a/span')
# # 或
# # v = item.xpath('*/a/span')
# print(v)