400 Bad request on python requests.get() - python-requests

Question

I am doing a bit of web scraping with political donations and have a link that I am scraping from one page than I then need to scrape. I can get the secondary links just fine, however when i try to send a requests.get() call, the html returned from the call gives me a bad request 400 error.
I've already tried to change the request around by changing or adding more headers but nothing seems to work.
headers = {
"Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8",
"Accept - Encoding": "gzip, deflate",
"Accept-Language": "en-US,en;q=0.9",
"Cache - Control": "max - age = 0",
"Connection": "keep-alive",
"DNT": "1",
"Host": "docquery.fec.gov",
"Referer": "http://www.politicalmoneyline.com/tr/tr_MG_IndivDonor.aspx?tm=3",
"Upgrade-Insecure-Requests": "1",
"User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.98 Safari/537.36"
}
params = {
"14960391627": ""
}
pdf_page = requests.get(potential_donor[10], headers=headers, params=params)
html = pdf_page.text
soup_donor_page = BeautifulSoup(html, 'html.parser')
print(soup_donor_page)
note: the url of the sites should look something like this:
http://docquery.fec.gov/cgi-bin/fecimg/?14960391627
with the ending digits being different
The output of the print(soup_donor_page) is:
400 Bad request
Your browser sent an invalid request.
I need to get the actual html of the page in order to grab the embedded pdf from the page.

Answer 1

I suspect the cause is an issue with requests that arises when it is provided a parameter without a value.
Try building the url with a format string instead:
import requests
from bs4 import BeautifulSoup
headers = {
"User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.98 Safari/537.36"
}
param = "14960391627"
r = requests.get(f"http://docquery.fec.gov/cgi-bin/fecimg/?{param}", headers=headers)
soup = BeautifulSoup(r.content, "html.parser")
print(soup.find("embed")["src"])
Result:
http://docquery.fec.gov/pdf/859/14960388859/14960388859_002769.pdf#zoom=fit&navpanes=0