如何写一个文件作为我的打印？

Question

我用bs4编写了一个Python 3程序，以便成功获取维基百科的子类别。现在，我可以看到打印结果，但我无法将结果写入文件。

from bs4 import BeautifulSoup 
import requests 
import csv 

url = 'https://en.wikipedia.org/wiki/Category:proprietary software' 
content = requests.get(url).content 
soup = BeautifulSoup(content,'lxml') 
noOFsubcategories = soup.find('p') 
print('------------------------------------------------------------------') 
print(noOFsubcategories.text+'------------------------------------------------------------------') 
tag = soup.find('div', {'class' : 'mw-category'}) 
links = tag.findAll('a') 
#print(links) 

counter = 1 
for link in links: 
    print (str(counter) + " " + link.text) 
    counter = counter + 1 

with open('subcategories.csv', 'a') as f: 
    f.write(links) 

Answer 1

只是一个小变化，循环下把写，每个循环都会写一个链接到文件

counter = 1 
for link in links: 
    print (str(counter) + " " + link.text) 
    counter = counter + 1 
    with open('subcategories.csv', 'a') as f: 
     f.write(link['href'].split(':')[1]+'\n') 

出来：

/wiki/Category:Formerly_proprietary_software 
/wiki/Category:Freeware 
/wiki/Category:Oracle_software 
/wiki/Category:Proprietary_cross-platform_software 
/wiki/Category:Proprietary_database_management_systems 
/wiki/Category:Proprietary_operating_systems 
/wiki/Category:Proprietary_version_control_systems 
/wiki/Category:Proprietary_wiki_software 
/wiki/Category:Shareware 
/wiki/Category:VMware 
/wiki/Category:Warez 

更好：

# do not need to open file in each loop, just put it above loop 
counter = 1 
with open('subcategories.csv', 'a') as f: 
    for link in links: 
     print (str(counter) + " " + link.text) 
     counter = counter + 1 
     f.write(link['href']+'\n') 

Answer 2

首先初始化列表与索引和链接文本列表，然后使用csv.writer写入csv文件。注意下面的使用enumerate()：

links = [[index, a.get_text()] for index, a in enumerate(tag.find_all('a'), start=1)] 

with open('subcategories.csv', 'a') as f: 
    writer = csv.writer(f) 
    writer.writerows(links) 

---

而且，您可以通过使用单个CSS selector提高你定位的子类别的方式：

soup.select("div.mw-category a") 

---

完整的代码我m执行：

import csv 

from bs4 import BeautifulSoup 
import requests 


url = 'https://en.wikipedia.org/wiki/Category:proprietary software' 
content = requests.get(url).content 
soup = BeautifulSoup(content, 'lxml') 
noOFsubcategories = soup.find('p') 

tag = soup.find('div', {'class': 'mw-category'}) 

links = [[index, a.get_text()] for index, a in enumerate(tag.find_all('a'), start=1)] 

with open('subcategories.csv', 'a') as f: 
    writer = csv.writer(f) 
    writer.writerows(links) 

运行此代码后的subcategories.csv内容是：

1,Formerly free software 
2,Formerly proprietary software 
3,Freeware 
4,Oracle software 
5,Proprietary cross-platform software 
6,Proprietary database management systems 
7,Proprietary operating systems 
8,Proprietary version control systems 
9,Proprietary wiki software 
10,Shareware 
11,VMware 
12,Warez