使用 beautifulsoup 抓取 XML 元素属性答案

【问题标题】：Scraping XML element attributes with beautifulsoup使用 beautifulsoup 抓取 XML 元素属性
【发布时间】：2023-03-09 15:17:01
【问题描述】：

我有以下代码：

from urllib.request import urlopen
from bs4 import BeautifulSoup
html = urlopen("https://api.stlouisfed.org/fred/...")
bsObj = BeautifulSoup(html.read(), "lxml");

print(bsObj)

它返回如下内容：

<?xml version="1.0" encoding="utf-8" ?><html><body><observations count="276" file_type="xml" limit="100000" observation_end="9999-12-31" observation_start="1776-07-04" offset="0" order_by="observation_date" output_type="1" realtime_end="2016-06-22" realtime_start="2016-06-22" sort_order="asc" units="lin">
<observation date="1947-04-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="-0.4"></observation>
<observation date="1947-07-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="-0.4"></observation>
<observation date="1947-10-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="6.4"></observation>
<observation date="1948-01-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="6"></observation>
<observation date="1948-04-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="6.7"></observation>
<observation date="1948-07-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="2.3"></observation>
<observation date="1948-10-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="0.4"></observation>
<observation date="1949-01-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="-5.4"></observation>
<observation date="1949-04-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="-1.3"></observation>
<observation date="1949-07-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="4.5"></observation>
<observation date="1949-10-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="-3.5"></observation>
<observation date="1950-01-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="16.9"></observation>
<observation date="1950-04-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="12.7"></observation>
<observation date="1950-07-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="16.3"></observation>
</observations>
</body></html>

我只想提取“日期”和“值”，所以最后我有这样的东西：

1947-04-01 -0.4
1947-07-01 -0.4
1947-10-01 6.4
1948-01-01 6
and so on...

到目前为止，我使用 replace 来抓取文本，并使用 import csv 来抓取 csv 文件：

string = str(bsObj)

string = string.replace("realtime_start=","")
string = string.replace("realtime_end=","")
string = string.replace("observation","")
string = string.replace("date=","")
string = string.replace('"2016-06-22"',"")
string = string.replace("value=","")
string = string.replace("<","")
string = string.replace(">","")
string = string.replace("/","")
string = string.replace('"',"")
print(string)

import csv
with open('test.csv', 'w', newline='') as fp:
    a = csv.writer(fp, delimiter=',')
    data = string
    a.writerows(data)

这几乎是一场灾难。它将文本推入 csv，但每个 simbol 都会进入新行。

我想知道是否有任何更优雅的方式可以提取我需要的内容。例如：

for line in f:
   extract "date" and "value"

或类似的。将其插入 .csv 文件的最合适方法是什么？每次调用此脚本时，我都会重写 .csv 文件。字段必须用“，”分隔，行用“/n”分隔。

【问题讨论】：

标签： python python-3.x csv beautifulsoup elementtree

【解决方案1】：

上面的效果很好！如果您想使用 URL 而不是本地文件，代码将如下所示：

from bs4 import BeautifulSoup
from urllib.request import urlopen
html = urlopen("https://api.stlouisfed.org/fred/series/.......")
bsObj = BeautifulSoup(html.read(), "lxml");

for ob in bsObj.find_all("observation"):
    print(ob["date"])
    print(ob["value"])

对于 .csv：

import csv
with open("out.csv", "w") as f:
    csv.writer(f).writerows((ob["date"], ob["value"])
                            for ob in bsObj.find_all("observation"))

【讨论】：

【解决方案2】：

找到所有的属性标签，然后提取你想要的属性：

x = """<?xml version="1.0" encoding="utf-8" ?><html><body><observations count="276" file_type="xml" limit="100000" observation_end="9999-12-31" observation_start="1776-07-04" offset="0" order_by="observation_date" output_type="1" realtime_end="2016-06-22" realtime_start="2016-06-22" sort_order="asc" units="lin">
<observation date="1947-04-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="-0.4"></observation>
<observation date="1947-07-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="-0.4"></observation>
<observation date="1947-10-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="6.4"></observation>
<observation date="1948-01-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="6"></observation>
<observation date="1948-04-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="6.7"></observation>
<observation date="1948-07-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="2.3"></observation>
<observation date="1948-10-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="0.4"></observation>
<observation date="1949-01-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="-5.4"></observation>
<observation date="1949-04-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="-1.3"></observation>
<observation date="1949-07-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="4.5"></observation>
<observation date="1949-10-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="-3.5"></observation>
<observation date="1950-01-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="16.9"></observation>
<observation date="1950-04-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="12.7"></observation>
<observation date="1950-07-01" realtime_end="2016-06-22" realtime_start="2016-06-22" value="16.3"></observation>
</observations>
</body></html>"""

from bs4 import BeautifulSoup

soup = BeautifulSoup(x,"lxml")

for ob in soup.find_all("observation"):
    print(ob["date"])
    print(ob["value"])

这会给你：

1947-04-01
-0.4
1947-07-01
-0.4
1947-10-01
6.4
1948-01-01
6
1948-04-01
6.7
1948-07-01
2.3
1948-10-01
0.4
1949-01-01
-5.4
1949-04-01
-1.3
1949-07-01
4.5
1949-10-01
-3.5
1950-01-01
16.9
1950-04-01
12.7
1950-07-01
16.3

要写入 csv：

from bs4 import BeautifulSoup
import csv

soup = BeautifulSoup(x, "lxml")
with open("out.csv", "w") as f:
    csv.writer(f).writerows((ob["date"], ob["value"])
                            for ob in soup.find_all("observation"))

这会给你一个 csv 文件：

1947-04-01,-0.4
1947-07-01,-0.4
1947-10-01,6.4
1948-01-01,6
1948-04-01,6.7
1948-07-01,2.3
1948-10-01,0.4
1949-01-01,-5.4
1949-04-01,-1.3
1949-07-01,4.5
1949-10-01,-3.5
1950-01-01,16.9
1950-04-01,12.7
1950-07-01,16.3

【讨论】：