Python Web Scraping using BS - python-3.x

Question

I have a web scraping program that gets multiple pages, but I have to set the while loop to a number. I want to make a condition that stops the loop once it reaches the last page or recognizes there are no more items to scrape. Assume I don't know how many pages exist. How do I change the while loop condition to make it stop without putting a random number?
import requests
from bs4 import BeautifulSoup
import csv
filename="output.csv"
f=open(filename, 'w', newline="",encoding='utf-8')
headers="Date, Location, Title, Price\n"
f.write(headers)
i=0
while i<5000:
if i==0:
page_link="https://portland.craigslist.org/search/sss?query=xbox&sort=date"
else:
page_link="https://portland.craigslist.org/search/sss?s={}&query=xbox&sort=date".format(i)
res=requests.get(page_link)
soup=BeautifulSoup(res.text,'html.parser')
for container in soup.select('.result-info'):
date=container.select('.result-date')[0].text
try:
location=container.select('.result-hood')[0].text
except:
try:
location=container.select('.nearby')[0].text
except:
location='NULL'
title=container.select('.result-title')[0].text
try:
price=container.select('.result-price')[0].text
except:
price="NULL"
print(date,location,title,price)
f.write(date+','+location.replace(","," ")+','+title.replace(","," ")+','+price+'\n')
i+=120
f.close()

Answer 1

I use while True to run endless loop and break to exit when there is no data
data = soup.select('.result-info')
if not data:
print('END: no data:')
break
I use module csv to save data so I don't have to use replace(","," ").
It will put text in " " if there is , in text.
s={} can be in any place after ? so I put it at the end to make code more readable.
Portal gives first page even if you use s=0 so I don't have to check i == 0
(BTW: in my code it has more readable name offset)
Full code.
import requests
from bs4 import BeautifulSoup
import csv
filename = "output.csv"
f = open(filename, 'w', newline="", encoding='utf-8')
csvwriter = csv.writer(f)
csvwriter.writerow( ["Date", "Location", "Title", "Price"] )
offset = 0
while True:
print('offset:', offset)
url = "https://portland.craigslist.org/search/sss?query=xbox&sort=date&s={}".format(offset)
response = requests.get(url)
if response.status_code != 200:
print('END: request status:', response.status)
break
soup = BeautifulSoup(response.text, 'html.parser')
data = soup.select('.result-info')
if not data:
print('END: no data:')
break
for container in data:
date = container.select('.result-date')[0].text
try:
location = container.select('.result-hood')[0].text
except:
try:
location = container.select('.nearby')[0].text
except:
location = 'NULL'
#location = location.replace(","," ") # don't need it with `csvwriter`
title = container.select('.result-title')[0].text
try:
price = container.select('.result-price')[0].text
except:
price = "NULL"
#title.replace(",", " ") # don't need it with `csvwriter`
print(date, location, title, price)
csvwriter.writerow( [date, location, title, price] )
offset += 120
f.close()