使用python请求屏蔽为浏览器并下载文件

Question

我正试图使用python请求库从以下链接下载文件：http://www.nasdaq.com/screening/companies-by-industry.aspx?exchange=NASDAQ&render=下载

只有在使用浏览器时，单击此链接才会给您一个文件（纳斯达克.csv）。我使用Firefox网络监视器Ctrl-Shift-Q来检索Firefox发送的所有标头。所以现在我终于得到了200服务器的响应，但仍然没有文件。此脚本生成的文件包含纳斯达克网站的部分内容，而不是csv数据。我在这个网站上看到了类似的问题，没有什么让我相信这在请求库中是不可能的。

代码：

import requests
url = "http://www.nasdaq.com/screening/companies-by-industry.aspx?exchange=NASDAQ&render=download"
# Fake Firefox headers 
headers = {"Host" : "www.nasdaq.com", 
        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:42.0) Gecko/20100101 Firefox/42.0", 
        "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8", 
        "Accept-Language": "en-US,en;q=0.5", 
        "Accept-Encoding": "gzip, deflate", 
        "DNT": "1", 
        "Cookie": "clientPrefs=||||lightg; userSymbolList=EOD+&DIT; userCookiePref=true; selectedsymbolindustry=EOD,; selectedsymboltype=EOD,EVERGREEN GLOBAL DIVIDEND OPPORTUNITY FUND COMMON SHARES OF BENEFICIAL INTEREST,NYSE; c_enabled$=true", 
        "Connection": "keep-alive", }
# Get the list
response = requests.get(url, headers, stream=True)
print(response.status_code)
# Write server response to file
with open("nasdaq.csv", 'wb') as f:
        for chunk in response.iter_content(chunk_size=1024): 
            if chunk: # filter out keep-alive new chunks
                f.write(chunk)

Answer 1

您不需要提供任何标头：

import requests
url = "http://www.nasdaq.com/screening/companies-by-industry.aspx?exchange=NASDAQ&render=download"
response = requests.get(url, stream=True)
print(response.status_code)
# Write server response to file
with open("nasdaq.csv", 'wb') as f:
    for chunk in response.iter_content(chunk_size=1024):
        if chunk: # filter out keep-alive new chunks
            f.write(chunk)

你也可以只写内容：

import requests
# Write server response to file
with open("nasdaq.csv", 'wb') as f:
       f.write(requests.get(url).content)

或者使用urlib:

urllib.urlretrieve("http://www.nasdaq.com/screening/companies-by-industry.aspx?exchange=NASDAQ&render=download","nasdaq.csv")

所有方法都会为您提供3137行的csv文件：

"Symbol","Name","LastSale","MarketCap","ADR TSO","IPOyear","Sector","Industry","Summary Quote",
"TFSC","1347 Capital Corp.","9.79","58230920","n/a","2014","Finance","Business Services","http://www.nasdaq.com/symbol/tfsc",
"TFSCR","1347 Capital Corp.","0.15","0","n/a","2014","Finance","Business Services","http://www.nasdaq.com/symbol/tfscr",
"TFSCU","1347 Capital Corp.","10","41800000","n/a","2014","Finance","Business Services","http://www.nasdaq.com/symbol/tfscu",
"TFSCW","1347 Capital Corp.","0.178","0","n/a","2014","Finance","Business Services","http://www.nasdaq.com/symbol/tfscw",
"PIH","1347 Property Insurance Holdings, Inc.","7.51","46441171.61","n/a","2014","Finance","Property-Casualty Insurers","http://www.nasdaq.com/symbol/pih",
"FLWS","1-800 FLOWERS.COM, Inc.","7.87","510463090.04","n/a","1999","Consumer Services","Other Specialty Stores","http://www.nasdaq.com/symbol/flws",
"FCTY","1st Century Bancshares, Inc","7.81","80612492.62","n/a","n/a","Finance","Major Banks","http://www.nasdaq.com/symbol/fcty",
"FCCY","1st Constitution Bancorp (NJ)","12.39","93508122.96","n/a","n/a","Finance","Savings Institutions","http://www.nasdaq.com/symbol/fccy",
"SRCE","1st Source Corporation","30.54","796548769.38","n/a","n/a","Finance","Major Banks","http://www.nasdaq.com/symbol/srce",
"VNET","21Vianet Group, Inc.","20.26","1035270865.78","51099253","2011","Technology","Computer Software: Programming, Data Processing","http://www.nasdaq.com/symbol/vnet",
   ...................................

如果由于某种原因它不适用于您，那么您可能需要升级您的请求版本。

Answer 2

您实际上并不需要这些标头。您甚至不需要保存到文件中。

import requests
import csv
url = "http://www.nasdaq.com/screening/companies-by-industry.aspx?exchange=NASDAQ&render=download"
response = requests.get(url)
data = csv.DictReader(response.content.splitlines())
for row in data:
    print row

样本输出：

{'Sector': 'Technology', 'LastSale': '2.46', 'Name': 'Zynga Inc.', '': '', 'Summary Quote': 'http://www.nasdaq.com/symbol/znga', 'Symbol': 'ZNGA', 'Industry': 'EDP Services', 'MarketCap': '2295110123.7', 'IPOyear': '2011', 'ADR TSO': 'n/a'}

如果您愿意，可以使用csv.reader而不是DictReader。

Answer 3

这个问题的另一种更短的解决方案是：

import urllib
downloadFile = urllib.URLopener()
downloadFile.retrieve("http://www.nasdaq.com/screening/companies-by-industry.aspx?exchange=NASDAQ&render=download", "companylist.csv")

此代码使用URL库创建URL请求对象（downloadFile），然后从NASDAQ链接检索数据并将其保存为companylist.csv。

根据Python文档，如果要发送自定义用户代理（如Firefox用户代理），可以将URLopener子类化，并将version属性设置为要使用的用户代理。

注意：根据Python文档，自Python v3.3起，urllib.URLopener()已弃用。因此，它最终可能会从Python标准中删除。然而，从Pythonv3.6（Dev）开始，urllib.URLopener()仍然被支持作为遗留接口