Python网络爬虫学习笔记（十）：PyQuery库的使用

文章目录

1.初始化
- 1.1 字符串初始化
- 1.2 URL初始化
- 1.3 文件初始化
2.CSS选择器
3.查找节点
- 3.1 子节点
- 3.2 父节点
- 3.3 兄弟节点
- - 遍历
4.获取信息
- 4.1 获取属性
- 4.2 获取文本
5.节点操作

1.初始化

1.1 字符串初始化

引入PyQuery对象，取别名为pq。声明一个HTML字符串，并将其当作参数传递给PyQuery类，这样就成功完成了初始化。传入li节点，这样就可以选择所有的li节点：

from pyquery import PyQuery as pqhtml = '''
<div><ul><li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li></ul></div>
'''
doc = pq(html)
print(type(doc))
print(doc)
print(doc('li'))

<class 'pyquery.pyquery.PyQuery'>
<div><ul><li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li></ul></div>
<li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li>

1.2 URL初始化

指定参数url初始化：

from pyquery import PyQuery as pq
doc = pq(url = 'http://cuiqingcai.com')
print(doc('title'))

<title>静觅丨崔庆才的个人博客</title>

1.3 文件初始化

传递本地的文件名，此时将参数指定为filename：

from pyquery import PyQuery as pq
doc = pq(filename='demo.html')
print(doc('li'))

2.CSS选择器

html = '''
<div id="container"><ul class="list"><li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li></ul></div>
'''
from pyquery import PyQuery as pq
doc = pq(html)
print(doc('#container .list li'))
print(type(doc('#container .list li')))

<li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li><class 'pyquery.pyquery.PyQuery'>

这里我们初始化PyQuery对象之后，传入了一个CSS选择器#container .list li，它的意思是先选取id为container的节点，然后再选取其内部的class为list的节点内部的所有li节点。然后，打印输出

3.查找节点

3.1 子节点

查找子节点时，需要用到find()方法，此时传入的参数是CSS选择器：

from pyquery import PyQuery as pq
doc = pq(html)
items = doc('.list')
print(type(items))
print(items)
lis = items.find('li')
print(type(lis))
print(lis)

<class 'pyquery.pyquery.PyQuery'>
<ul class="list"><li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li></ul><class 'pyquery.pyquery.PyQuery'>
<li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li>

find()的查找范围是节点的所有子孙节点，而如果我们只想查找子节点，那么可以用children()方法:

lis = items.children()
print(type(lis))
print(lis)

<class 'pyquery.pyquery.PyQuery'>
<li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li>

如果要筛选所有子节点中符合条件的节点，比如想筛选出子节点中class为active的节点，可以向children()方法传入CSS选择器.active：

lis = items.children('.active')
print(lis)

<li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li>

3.2 父节点

我们可以使用parent()方法来获取某个节点的父节点:

html = '''
<div class="wrap"><div id="container"><ul class="list"><li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li></ul></div></div>
'''
from pyquery import PyQuery as pq
doc = pq(html)
items = doc('.list')
container = items.parent()
print(type(container))
print(container)

<class 'pyquery.pyquery.PyQuery'>
<div id="container"><ul class="list"><li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li></ul></div>

可以使用parents()方法获取所有的祖先节点

from pyquery import PyQuery as pq
doc = pq(html)
items = doc('.list')
parents = items.parents()
print(type(parents))
print(parents)

<class 'pyquery.pyquery.PyQuery'>
<div class="wrap"><div id="container"><ul class="list"><li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li></ul></div></div><div id="container"><ul class="list"><li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li></ul></div>

向parents()方法传入CSS选择器筛选某个祖先节点:

parent = items.parents('.wrap')
print(parent)

<div class="wrap"><div id="container"><ul class="list"><li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li></ul></div></div>

3.3 兄弟节点

使用siblings()方法获取兄弟节点：

from pyquery import PyQuery as pq
doc = pq(html)
li = doc('.list .item-0.active')
print(li.siblings())

<li class="item-1"><a href="link2.html">second item</a></li><li class="item-0">first item</li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li>

向siblings方法传入CSS选择器筛选某个兄弟节点：

from pyquery import PyQuery as pq
doc = pq(html)
li = doc('.list .item-0.active')
print(li.siblings('.active'))

<li class="item-1 active"><a href="link4.html">fourth item</a></li>

遍历

对于多个节点的结果，需要遍历来获取。例如，这里把每一个li节点进行遍历，需要调用items()方法：

from pyquery import PyQuery as pq
doc = pq(html)
lis = doc('li').items()
print(type(lis))
for li in lis:print(li, type(li))

<class 'generator'>
<li class="item-0">first item</li><class 'pyquery.pyquery.PyQuery'>
<li class="item-1"><a href="link2.html">second item</a></li><class 'pyquery.pyquery.PyQuery'>
<li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><class 'pyquery.pyquery.PyQuery'>
<li class="item-1 active"><a href="link4.html">fourth item</a></li><class 'pyquery.pyquery.PyQuery'>
<li class="item-0"><a href="link5.html">fifth item</a></li><class 'pyquery.pyquery.PyQuery'>

4.获取信息

4.1 获取属性

调用attr()方法来获取属性:

html = '''
<div class="wrap"><div id="container"><ul class="list"><li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li></ul></div></div>
'''
from pyquery import PyQuery as pq
doc = pq(html)
a = doc('.item-0.active a')
print(a, type(a))
print(a.attr('href'))

<a href="link3.html"><span class="bold">third item</span></a> <class 'pyquery.pyquery.PyQuery'>
link3.html

此外，也可以通过调用attr属性来获取属性，用法如下：

print(a.attr.href)

link3.html

如果选中的是多个元素，然后调用attr()方法,只会得到第一个节点的属性:

a = doc('a')
print(a, type(a))
print(a.attr('href'))
print(a.attr.href)

<a href="link2.html">second item</a><a href="link3.html"><span class="bold">third item</span></a><a href="link4.html">fourth item</a><a href="link5.html">fifth item</a> <class 'pyquery.pyquery.PyQuery'>
link2.html
link2.html

遇到这种情况时，如果想获取所有的a节点的属性，就要用到前面所说的遍历了：

from pyquery import PyQuery as pq
doc = pq(html)
a = doc('a')
for item in a.items():print(item.attr('href'))

link2.html
link3.html
link4.html
link5.html

4.2 获取文本

可以调用text()方法来实现：

html = '''
<div class="wrap"><div id="container"><ul class="list"><li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li></ul></div></div>
'''
from pyquery import PyQuery as pq
doc = pq(html)
a = doc('.item-0.active a')
print(a)
print(a.text())

<a href="link3.html"><span class="bold">third item</span></a>
third item

但如果想要获取这个节点内部的HTML文本，就要用html()方法了：

from pyquery import PyQuery as pq
doc = pq(html)
li = doc('.item-0.active')
print(li)
print(li.html())

<li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><a href="link3.html"><span class="bold">third item</span></a>

如果我们选中的结果是多个节点，text()或html()会返回什么内容？我们用实例来看一下：

html = '''
<div class="wrap"><div id="container"><ul class="list"><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li></ul></div></div>
'''
from pyquery import PyQuery as pq
doc = pq(html)
li = doc('li')
print(li.html())
print(li.text())
print(type(li.text()))

<a href="link2.html">second item</a>
second item third item fourth item fifth item
<class 'str'>

html()方法返回的是第一个li节点的内部HTML文本，而text()则返回了所有的li节点内部的纯文本，中间用一个空格分割开，即返回结果是一个字符串。

5.节点操作

addClass和removeClass：

html = '''
<div class="wrap"><div id="container"><ul class="list"><li class="item-0">first item</li><li class="item-1"><a href="link2.html">second item</a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-1 active"><a href="link4.html">fourth item</a></li><li class="item-0"><a href="link5.html">fifth item</a></li></ul></div></div>
'''
from pyquery import PyQuery as pq
doc = pq(html)
li = doc('.item-0.active')
print(li)
li.removeClass('active')
print(li)
li.addClass('active')
print(li)

<li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-0"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li>

首先选中了第三个li节点，然后调用removeClass()方法，将li节点的active这个class移除，后来又调用addClass()方法，将class添加回来。每执行一次操作，就打印输出当前li节点的内容。

除了操作class这个属性外，也可以用attr()方法对属性进行操作。此外，还可以用text()和html()方法来改变节点内部的内容。示例如下：

html = '''
<ul class="list"><li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li>
</ul>
'''
from pyquery import PyQuery as pq
doc = pq(html)
li = doc('.item-0.active')
print(li)
li.attr('name', 'link')
print(li)
li.text('changed item')
print(li)
li.html('<span>changed item</span>')
print(li)

<li class="item-0 active"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-0 active" name="link"><a href="link3.html"><span class="bold">third item</span></a></li><li class="item-0 active" name="link">changed item</li><li class="item-0 active" name="link"><span>changed item</span></li>