Scraping: issues receiving table data when looping with request - python-3.x

Question

UPDATE:
The code only works momentarily. There are 2000+ cryptos and at this moment i have 492 unique files with their history.
When I try to run a url getting skipped in the first place on its own, it works. Therefore I think it has been narrowed down to have something to do with the request of content.
Is it possible to make sure the table i'm interested in is fully loaded before continuing the code?
UPDATE:
I got it working properly. I think there is a limit of requests you can do per sec or min on the website im trying to scrape from.
I put in a delay on 3 sec between every request and NOW IT WORKS!!!!
Thanks to both of you for the help. Even though it didn't provide a direct answer, it put me on the right track to figuring it out.
from bs4 import BeautifulSoup
import requests
import pandas as pd
import time
def scraping(url):
global line
content = requests.get(url).content
soup = BeautifulSoup(content,'html.parser')
table = soup.find('table', {'class': 'table'})
if not table:
print(url)
return
data = [[td.text.strip() for td in tr.findChildren('td')] for tr in table.findChildren('tr')]
df = pd.DataFrame(data)
df.drop(df.index[0], inplace=True)
df[0] = pd.to_datetime(df[0])
for i in range(1,7):
df[i] = pd.to_numeric(df[i].str.replace(",","").str.replace("-",""))
df.columns = ['Date','Open','High','Low','Close','Volume','Market Cap']
df.set_index('Date',inplace=True)
df.sort_index(inplace=True)
return df.to_csv(line + '_historical_data.csv')
with open("list_of_urls.txt") as file:
for line in file:
time.sleep(3)
line = line.strip()
start = "https://coinmarketcap.com/currencies/"
end = "/historical-data/?start=20000101&end=21000101"
url = start + line + end
scraping(url)

Answer 1

it could be URL not found 404 or the page has no table. To debug normalize your loop and print current processing Crypto name
table = soup.find('table', {'class': 'table'})
if not table:
print('no table')
return

Answer 2

You may perform findChildren() only of the returned table and tr objects are not NoneType, as follows:
data = [[td.text.strip() for td in tr.findChildren('td') if td] for tr in table.findChildren('tr') if tr] if table else []
if len(data) > 0:
# process your data here
Hope it helps.