Question

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>

我想只提取＆＃34; date＆＃34;和＆＃34;价值＆＃34;最后我有这样的事情：

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，import csv使用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)

这个虽然几乎是灾难。它将文本推送到csv，但每个simbol都会进入新行。

我想知道是否有更优雅的方式可以提取我需要的东西。例如：

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

或类似的。将它插入.csv文件的最合适的方法是什么？每次调用此脚本时，我都会重写.csv文件。字段必须用＆＃34;，＆＃34;分隔。和＆＃34; / n＆＃34;。

Answer 1

查找所有属性标记，然后只提取所需的属性：

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"])

哪个会给你：

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

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"))

它为您提供了一个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

Answer 2

以上作品很棒！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"])

和.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"))

使用beautifulsoup刮取XML元素属性

2 个答案: