【Python网络爬虫】150讲轻松搞定Python网络爬虫付费课程笔记 篇九——搜索文档树find_all 和 select方法

1. find 和find_all方法

1.1 find和find_all方法

• find方法，找到第一个满足条件的标签后立即返回，只返回一个元素
• find_all方法，找到所有满足条件的标签都返回回去，以列表形式返回很多元素

a_list = soup.find_all('a')
for a in a_list:
    # 1.
    # href = a['href']
    # print(href)
#    2.
    href = a.attrs['href']
    print(href)

1.2 使用find和find_all的过滤条件

• 关键字参数：将属性的名字作为关键字参数的名字，以及属性的值作为关键数参数的值进行过滤
• attrs参数：将属性条件放到字典中传给attrs参数

trs1 = soup.find_all('tr', class_='even')  #attrs={'class': 'even}
for tr in trs1:
    print(tr)

# 6.获取所有职位信息
trs2 = soup.find_all('tr')[1:]
lists = []
for tr in trs2:
    # tds = tr.find_all('td')
    # name = tds[0].string
    # category = tds[1].string
    # info = {}
    # info['name'] = name
    # info['category'] = category
    # list.append(info)

    infos = list(tr.stripped_strings)
    print(infos)

# print(lists)

from bs4 import BeautifulSoup

html = """
<table class="tablelist" cellpadding="0" cellspacing="0">
    <tbody>
        <tr class="h">
            <td class="l" width="374">职位名称</td>
            <td>职位类别</td>
            <td>人数</td>
            <td>地点</td>
            <td>发布时间</td>
        </tr>
        <tr class="even">
            <td class="l square"><a target="_blank" href="position_detail.php?id=33824&keywords=python&tid=87&lid=2218">22989-金融云区块链高级研发工程师（深圳）</a></td>
            <td>技术类</td>
            <td>1</td>
            <td>深圳</td>
            <td>2017-11-25</td>
        </tr>
        <tr class="odd">
            <td class="l square"><a target="_blank" href="position_detail.php?id=29938&keywords=python&tid=87&lid=2218">22989-金融云高级后台开发</a></td>
            <td>技术类</td>
            <td>2</td>
            <td>深圳</td>
            <td>2017-11-25</td>
        </tr>
        <tr class="even">
            <td class="l square"><a target="_blank" href="position_detail.php?id=31236&keywords=python&tid=87&lid=2218">SNG16-腾讯音乐运营开发工程师（深圳）</a></td>
            <td>技术类</td>
            <td>2</td>
            <td>深圳</td>
            <td>2017-11-25</td>
        </tr>
        <tr class="odd">
            <td class="l square"><a target="_blank" href="position_detail.php?id=31235&keywords=python&tid=87&lid=2218">SNG16-腾讯音乐业务运维工程师（深圳）</a></td>
            <td>技术类</td>
            <td>1</td>
            <td>深圳</td>
            <td>2017-11-25</td>
        </tr>
        <tr class="even">
            <td class="l square"><a target="_blank" href="position_detail.php?id=34531&keywords=python&tid=87&lid=2218">TEG03-高级研发工程师（深圳）</a></td>
            <td>技术类</td>
            <td>1</td>
            <td>深圳</td>
            <td>2017-11-24</td>
        </tr>
        <tr class="odd">
            <td class="l square"><a target="_blank" href="position_detail.php?id=34532&keywords=python&tid=87&lid=2218">TEG03-高级图像算法研发工程师（深圳）</a></td>
            <td>技术类</td>
            <td>1</td>
            <td>深圳</td>
            <td>2017-11-24</td>
        </tr>
        <tr class="even">
            <td class="l square"><a target="_blank" href="position_detail.php?id=31648&keywords=python&tid=87&lid=2218">TEG11-高级AI开发工程师（深圳）</a></td>
            <td>技术类</td>
            <td>4</td>
            <td>深圳</td>
            <td>2017-11-24</td>
        </tr>
        <tr class="odd">
            <td class="l square"><a target="_blank" href="position_detail.php?id=32218&keywords=python&tid=87&lid=2218">15851-后台开发工程师</a></td>
            <td>技术类</td>
            <td>1</td>
            <td>深圳</td>
            <td>2017-11-24</td>
        </tr>
        <tr class="even">
            <td class="l square"><a target="_blank" href="position_detail.php?id=32217&keywords=python&tid=87&lid=2218">15851-后台开发工程师</a></td>
            <td>技术类</td>
            <td>1</td>
            <td>深圳</td>
            <td>2017-11-24</td>
        </tr>
        <tr class="odd">
            <td class="l square"><a id="test" class="test" target='_blank' href="position_detail.php?id=34511&keywords=python&tid=87&lid=2218">SNG11-高级业务运维工程师（深圳）</a></td>
            <td>技术类</td>
            <td>1</td>
            <td>深圳</td>
            <td>2017-11-24</td>
        </tr>
    </tbody>
</table>
"""

soup = BeautifulSoup(html, 'lxml')

# 1.获取所有tr标签
# print(soup.tr)
# print(soup.find('tr')) #都只能获取一个tr标签，所以需要用到find_all

# trs = soup.find_all('tr')
# for tr in trs:
#     print(tr)
#     print('-'*50)

# 2.获取第2个tr标签
# tr = soup.find_all('tr', limit=2)[1]
# print(tr)

# 3.获取所有class=even的标签
trs1 = soup.find_all('tr', class_='even')  #attrs={'class': 'even}
for tr in trs1:
    print(tr)

# 4.所有id=test, class=test的a的标签
# list = soup.find_all('a', id='test', class_='test')
# for a in list:
#     print(a)

# 5. 所有a标签的href
a_list = soup.find_all('a')
for a in a_list:
    # 1.
    # href = a['href']
    # print(href)
#    2.
    href = a.attrs['href']
    print(href)

# 6.获取所有职位信息
trs2 = soup.find_all('tr')[1:]
lists = []
for tr in trs2:
    # tds = tr.find_all('td')
    # name = tds[0].string
    # category = tds[1].string
    # info = {}
    # info['name'] = name
    # info['category'] = category
    # list.append(info)

    infos = list(tr.stripped_strings)
    print(infos)

# print(lists)

2. select 方法 

使用css选择器的语法，使用select方法更加方便。

具体方法：

from bs4 import BeautifulSoup

html = """
<table class="tablelist" cellpadding="0" cellspacing="0">
    <tbody>
        <tr class="h">
            <td class="l" width="374">职位名称</td>
            <td>职位类别</td>
            <td>人数</td>
            <td>地点</td>
            <td>发布时间</td>
        </tr>
        <tr class="even">
            <td class="l square"><a target="_blank" href="position_detail.php?id=33824&keywords=python&tid=87&lid=2218">22989-金融云区块链高级研发工程师（深圳）</a></td>
            <td>技术类</td>
            <td>1</td>
            <td>深圳</td>
            <td>2017-11-25</td>
        </tr>
        <tr class="odd">
            <td class="l square"><a target="_blank" href="position_detail.php?id=29938&keywords=python&tid=87&lid=2218">22989-金融云高级后台开发</a></td>
            <td>技术类</td>
            <td>2</td>
            <td>深圳</td>
            <td>2017-11-25</td>
        </tr>
        <tr class="even">
            <td class="l square"><a target="_blank" href="position_detail.php?id=31236&keywords=python&tid=87&lid=2218">SNG16-腾讯音乐运营开发工程师（深圳）</a></td>
            <td>技术类</td>
            <td>2</td>
            <td>深圳</td>
            <td>2017-11-25</td>
        </tr>
        <tr class="odd">
            <td class="l square"><a target="_blank" href="position_detail.php?id=31235&keywords=python&tid=87&lid=2218">SNG16-腾讯音乐业务运维工程师（深圳）</a></td>
            <td>技术类</td>
            <td>1</td>
            <td>深圳</td>
            <td>2017-11-25</td>
        </tr>
        <tr class="even">
            <td class="l square"><a target="_blank" href="position_detail.php?id=34531&keywords=python&tid=87&lid=2218">TEG03-高级研发工程师（深圳）</a></td>
            <td>技术类</td>
            <td>1</td>
            <td>深圳</td>
            <td>2017-11-24</td>
        </tr>
        <tr class="odd">
            <td class="l square"><a target="_blank" href="position_detail.php?id=34532&keywords=python&tid=87&lid=2218">TEG03-高级图像算法研发工程师（深圳）</a></td>
            <td>技术类</td>
            <td>1</td>
            <td>深圳</td>
            <td>2017-11-24</td>
        </tr>
        <tr class="even">
            <td class="l square"><a target="_blank" href="position_detail.php?id=31648&keywords=python&tid=87&lid=2218">TEG11-高级AI开发工程师（深圳）</a></td>
            <td>技术类</td>
            <td>4</td>
            <td>深圳</td>
            <td>2017-11-24</td>
        </tr>
        <tr class="odd">
            <td class="l square"><a target="_blank" href="position_detail.php?id=32218&keywords=python&tid=87&lid=2218">15851-后台开发工程师</a></td>
            <td>技术类</td>
            <td>1</td>
            <td>深圳</td>
            <td>2017-11-24</td>
        </tr>
        <tr class="even">
            <td class="l square"><a target="_blank" href="position_detail.php?id=32217&keywords=python&tid=87&lid=2218">15851-后台开发工程师</a></td>
            <td>技术类</td>
            <td>1</td>
            <td>深圳</td>
            <td>2017-11-24</td>
        </tr>
        <tr class="odd">
            <td class="l square"><a id="test" class="test" target='_blank' href="position_detail.php?id=34511&keywords=python&tid=87&lid=2218">SNG11-高级业务运维工程师（深圳）</a></td>
            <td>技术类</td>
            <td>1</td>
            <td>深圳</td>
            <td>2017-11-24</td>
        </tr>
    </tbody>
</table>
"""

soup = BeautifulSoup(html, 'lxml')

trs = soup.select('tr')
# print(trs)

trs1 = soup.select('tr')[1]
# print(trs1)

trs2 = soup.select('tr[class="even"]')
# print(trs2)

trs3 = soup.select('a')
for a in trs3:
    href = a['href']
    # print(href)


trs4 = soup.select('tr')
for tr in trs4:
    info = list(tr.stripped_strings)
    print(info)