Question

我正在做一项任务，我需要从现场网站上抓取信息。

为此我使用https://www.nintendo.com/games/nintendo-switch-bestsellers，需要抓取游戏标题，价格和图像来源。我有标题工作，但价格和图像来源只是重新调整空列表，但通过pythex它返回正确的答案。

这是我的代码：

from re import findall, finditer, MULTILINE, DOTALL
from urllib.request import urlopen

game_html_source = urlopen\
('https://www.nintendo.com/games/nintendo-switch-bestsellers').\
read().decode("UTF-8")

# game titles - working
game_title = findall(r'<h3 class="b3">([A-Z a-z:0-9]+)</h3>', game_html_source)
print(game_title)

# game prices - retuning empty-list
game_prices = findall(r'<p class="b3 row-price">(\$[.0-9]+)</p>', game_html_source)
print(game_prices)

# game images - returning empty list
game_images = findall(r'<img alt="[A-Z a-z:]+" src=("https://media.nintendo.com/nintendo/bin/[A-Za-z0-9-\/_]+.png")>',game_html_source)
print(game_images)

Answer 1

使用正则表达式解析HTML有太多陷阱可靠处理。 BeautifulSoup和其他HTML解析器通过构建完整的文档数据结构来工作，然后您可以导航以提取有趣的部分 - 它是彻底和全面的，但如果源中的任何地方存在某些错误的HTML，即使它位于你不关心的部分，它可以打败解析过程。 Pyparsing采用中间方法 - 您可以定义仅匹配所需位的迷你解析器，并跳过其他所有内容（这也简化了解析后导航）。为了解决HTML样式中的一些变量，pyparsing提供了一个函数makeHTMLTags，它为开始和结束标记返回一对pyparsing表达式：

foo_start, foo_end = pp.makeHTMLTags('foo')

foo_start将匹配：

<foo>
<foo/>
<foo class='bar'>
<foo href=something_not_in_quotes>

以及更多属性和空白的变体。

foo_start表达式（与所有pyparsing表达式一样）将返回ParseResults对象。这样可以轻松访问已解析标记的各个部分：

foo_data = foo_start.parseString("<foo img='bar.jpg'>")
print(foo_data.img)

对于您的Nintendo页面抓取工具，请参阅下面带注释的来源：

import pyparsing as pp

# define expressions to match opening and closing tags <h3>
h3, h3_end = pp.makeHTMLTags("h3")

# define a specific type of <h3> tag that has the desired 'class' attribute
h3_b3 = h3().addCondition(lambda t: t['class'] == "b3")

# similar for <p>
p, p_end = pp.makeHTMLTags("p")
p_b3_row_price = p().addCondition(lambda t: t['class'] == "b3 row-price")

# similar for <img>
img, _ = pp.makeHTMLTags("img")
img_expr = img().addCondition(lambda t: t.src.startswith("//media.nintendo.com/nintendo/bin"))

# define expressions to capture tag body for title and price - include negative lookahead for '<' so that
# tags with embedded tags are not matched
LT = pp.Literal('<')
title_expr = h3_b3 + ~LT + pp.SkipTo(h3_end)('title') + h3_end
price_expr = p_b3_row_price + ~LT + pp.SkipTo(p_end)('price') + p_end

# compose a scanner expression by '|'ing the 3 sub-expressions into one
scanner = title_expr | price_expr | img_expr

# not shown - read web page into variable 'html'

# use searchString to search through the retrieved HTML for matches
for match in scanner.searchString(html):
    if 'title' in match:
        print("Title:", match.title)
    elif 'price' in match:
        print("Price:", match.price)
    elif 'src' in match:
        print("Img src:", match.src)
    else:
        print("???", match.dump())

打印的前几场比赛是：

Img src: //media.nintendo.com/nintendo/bin/SF6LoN-xgX1iT617eWfBrNcWH6RQXnSh/I_IRYaBzJ61i-3hnYt_k7hVxHtqGmM_w.png
Title: Hyrule Warriors: Definitive Edition
Price: $59.99
Img src: //media.nintendo.com/nintendo/bin/wcfCyAd7t2N78FkGvEwCOGzVFBNQRbhy/AvG-_d4kEvEplp0mJoUew8IAg71YQveM.png
Title: Donkey Kong Country: Tropical Freeze
Price: $59.99
Img src: //media.nintendo.com/nintendo/bin/QKPpE587ZIA5fUhUL4nSbH3c_PpXYojl/J_Wd79pnFLX1NQISxouLGp636sdewhMS.png
Title: Wizard of Legend
Price: $15.99

RE在pythex中工作，但在python中不起作用

1 个答案: