Forum Thread: Efficient Python Based Crawler

i created a python crawler from scratch. it is very efficient ,-i tried to crawl many website (34) some of them are of, more then 400000 pages and it work like a charm. but sometimes it stuck in a loop by try to crawl single page again and again. so please help me to figure out the possible solution (my guess :- its may be because of the characters like -"\n" so how can i filter these type of characters) and its appreciable if test my script in different website and let me know ,if you find any error.

the best thing about my python crawler is that, you can also run it in parallel (i tested it by running 148 scripts in parallel works great and it saves time(as long as the website don't misunderstood crawling as DDOS attack))

its highly appreciable if you also provide me the solution of error ,you find .

i paste the code of my python script below. you can also download it from http://www.yourfilelink.com/get.php?fid=1397093

########################################################################################################################################################################################################################################################################################################################################################

from bs4 import BeautifulSoup
import requests
import MySQLdb as sql
import time
import warnings

print("starting")

warnings.filterwarnings('ignore')

db = sql.connect("localhost", "root", "arp", "website")
cursor = db.cursor()
db.autocommit(True)

print("connected to database")

url = "http://www.example.com"
extension = ".com"
print("scrapping url -",url)

r = requests.head(url)
cursor.execute("insert ignore into urls(urls,status,status_code) values(%s,'pending',%s)", url, r.status_code)

cursor.execute("select status from urls where status ='pending' limit 1")
result = str(cursor.fetchone())

while (result != "None"):

cursor.execute("select urls from urls where status ='pending' limit 1")
result = str(cursor.fetchone())

s_url = result2:-3

cursor.execute("update urls set status = 'done' where urls= %s ", s_url)

if "https" in url:
url1 = url12:
else:
url1 = url11:
zone = 0
while True:

try:
r = requests.get(s_url,timeout=60)
break

except:
if s_url == "":

print("done")
break
elif zone >= 4:
print("this url is not valid -",s_url)
break
else:
print("Oops! may be connection was refused. Try again...",s_url)
time.sleep(0.2)
zone = zone + 1

soup = BeautifulSoup(r.content.lower(), 'lxml')

links = soup.find_all("a")

for x in links:
a = x.get('href')
if a is not None and a != "":

if a != "" and a.find("\n") != -1:
a = a0:a.find("\n")

if a != "" and a-1 == "/":
a = a0:-1

if a != "":

common_extension = ',',' ',"#",'"','.mp3',"jpg",'.wav','.wma','.7z','.deb','.pkg','.rar','.rpm','.tar','.zip','.bin','.dmg','.iso','.toast','.vcd','.csv','.dat','.log','.mdb','.sav','.sql','.apk','.bat','.exe','.jar','.py','.wsf','.fon','.ttf','.bmp','.gif','.ico','.jpeg','.png','.part','.ppt','.pptx','.class','.cpp','.java','.swift','.ods','.xlr','.xls','.xlsx','.bak','.cab','.cfg','.cpl','.dll','.dmp','.icns','.ini','.lnk','.msi','.sys','.tmp','.3g2','.3gp','.avi','.flv','.h264','.m4v','.mkv','.mov','.mp4','.mpg','.vob','.wmv','.doc','.pdf','.txt'

for ext in common_extension:
if ext in a:
a = ""
break

if a != "":
if a0:5 == '/http':
a = a1:
if a0:6 == '//http':
a = a2:

if a0:len(url1) + 12 == "https://www ." + url1:
cursor.execute("insert ignore into urls(urls,status,status_code) values(%s,'pending',%s)",
a, r.status_code)
elif a0:len(url1) + 11 == "http://www ." + url1:
cursor.execute("insert ignore into urls(urls,status,status_code) values(%s,'pending',%s)",
a, r.status_code)
elif a0:len(url1) + 8 == "https://" + url1:
cursor.execute("insert ignore into urls(urls,status,status_code) values(%s,'pending',%s)",
url + (a[(a.find(extension + "/")) + 4:), r.status_code)
elif a0:len(url1) + 7 == "http://" + url1:
cursor.execute("insert ignore into urls(urls,status,status_code) values(%s,'pending',%s)",
url + (a[(a.find(extension + "/")) + 4:), r.status_code)
elif a0:2 == "//" and a0:3 != "///" and "." not in a and "http" not in a and "www." not in a:
cursor.execute("insert ignore into urls(urls,status,status_code) values(%s,'pending',%s)",
url + a[1:, r.status_code)
elif a0:1 == "/" and a0:2 != "//" and "." not in a and "http" not in a and "www." not in a:
cursor.execute("insert ignore into urls(urls,status,status_code) values(%s,'pending',%s)",
url + a[0:, r.status_code)
elif 'http' not in a and 'www.' n ot in a and "." not in a and a0 != "/":
cursor.execute("insert ignore into urls(urls,status,status_code) values(%s,'pending',%s)",
url + '/' + a, r.status_code)

cursor.execute("alter table urls drop id")
cursor.execute("alter table urls add id int primary key not null auto_increment first")
print("new id is created")

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