Почему парсер выдаёт 403 даже после указания Cookie и User-Agent?
Виной 403 коду является cloudflare.
Для обхода мне помог cfscrape
def get_session():
    session = requests.Session()
    session.headers = {
        'User-Agent':'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:69.0)   Gecko/20100101 Firefox/69.0',
        'Accept':'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
        'Accept-Language':'ru,en-US;q=0.5',
        'Accept-Encoding':'gzip, deflate, br',
        'DNT':'1',
        'Connection':'keep-alive',
        'Upgrade-Insecure-Requests':'1',
        'Pragma':'no-cache',
        'Cache-Control':'no-cache'}
    return cfscrape.create_scraper(sess=session)
session = get_session() # Дальше работать как с обычной requests.Session
Немного кода о выдёргивании прямых ссылок на хайрес пикчи:
Кодimport requests
import cfscrape

def get_session():
    session = requests.Session()
    session.headers = {
        'Host':'www.artstation.com',
        'User-Agent':'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:69.0)   Gecko/20100101 Firefox/69.0',
        'Accept':'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
        'Accept-Language':'ru,en-US;q=0.5',
        'Accept-Encoding':'gzip, deflate, br',
        'DNT':'1',
        'Connection':'keep-alive',
        'Upgrade-Insecure-Requests':'1',
        'Pragma':'no-cache',
        'Cache-Control':'no-cache'}
    return cfscrape.create_scraper(sess=session)

def artstation():
    url = 'https://www.artstation.com/kyuyongeom'
    page_url = 'https://www.artstation.com/users/kyuyongeom/projects.json'
    post_pattern = 'https://www.artstation.com/projects/{}.json'
    session = get_session()
    absolute_links = []

    response = session.get(page_url, params={'page':1}).json()
    pages, modulo = divmod(response['total_count'], 50)
    if modulo: pages += 1

    for page in range(1, pages+1):
        if page != 1:
            response = session.get(page_url, params={'page':page}).json()
        for post in response['data']:
            shortcode = post['permalink'].split('/')[-1]
            inner_resp = session.get(post_pattern.format(shortcode)).json()
            for img in inner_resp['assets']:
                if img['asset_type'] == 'image':
                    absolute_links.append(img['image_url'])

    with open('links.txt', 'w') as file:
        file.write('\n'.join(absolute_links))

if __name__ == '__main__':
    artstation()
Есть смысл указать все поля из Header, а не только User-Agent