Downloading Images - Unable to find correct selector

[Brompy]

I'm trying to write a script that 1) goes to a website 2) downloads and parses the HTML 3) downloads a comic image 4) selects the "previous comic button" 5) repeats 1-4

The script is failing on either hitting the "previous comic" button, or downloading the next page before it can reach the second image.

I have tried tinkering with the different selectors, but I'm not sure why it's not working.

#! python3
#swordscraper.py - Downloads all the swords comics.

import requests, os, bs4

os.chdir(r'C:\Users\bromp\OneDrive\Desktop\Python')
os.makedirs('swords', exist_ok=True) #store comics in /swords
url = 'https://swordscomic.com/' #starting url

while not url.endswith('#'):

     #Download the page.
    print('Downloading page %s...' % url)
    res = requests.get(url)
    res.raise_for_status

    soup = bs4.BeautifulSoup(res.text, 'html.parser') 

    #Find the URL of the comic image.
    comicElem = soup.select('#comic-image')
    if comicElem == []:
        print('Could not find comic image.')
    else:
        comicUrl = comicElem[0].get('src')
        comicUrl = "http://" + comicUrl
        if 'swords' not in comicUrl:
            comicUrl=comicUrl[:7]+'swordscomic.com/'+comicUrl[7:]
        #Download the image.
        print('Downloading image %s...' % (comicUrl))
        res = requests.get(comicUrl)
        res.raise_for_status()

    #Save the image to ./swords
    imageFile = open(os.path.join('swords', os.path.basename(comicUrl)), 'wb')
    for chunk in res.iter_content(100000):
        imageFile.write(chunk)
    imageFile.close()

    #Get the Prev button's url.
    prevLink = soup.select('a[id="navigation-previous"]')[1]
    url = 'https://swordscomic.com/' + prevLink.get('href')

This is the output it gives when I run it:

Downloading page https://swordscomic.com/...
Downloading image http://swordscomic.com//media/Swords364t.png...
Traceback (most recent call last):
  File "C:\Users\bromp\AppData\Local\Programs\Python\Python37-32\swordscraper.py", line 40, in <module>
    prevLink = soup.select('a[id="navigation-previous"]')[1]
IndexError: list index out of range

Do I need to use a different module, like Selenium?

[Larz60+]

I think you want to use selenium for this.
How-to do this:
web scraping part 1
web scraping part 2

[snippsat]

Can use Selenium,but it's a cooler way here as they use Roman numerals in url.
Then can write it so can use integer to navigate or eg download all images.
Example to get one image.

# roman.py
import requests
import os, re
from roman_convert import roman_to_int, int_to_roman

def make_url(roman_number):
    return f'https://swordscomic.com/comic/{roman_number}/'

def download(url, img_nr):
    img = requests.get(url)
    img_name = f'{int_to_roman(img_nr)}.png'
    with open(img_name, 'wb') as f_out:
        f_out.write(img.content)

if __name__ == '__main__':
    img_nr = 361
    url = f'https://swordscomic.com/media/Swords{img_nr}t.png'
    roman_number = int_to_roman(img_nr)
    org_link = make_url(roman_number)
    print(f'Dowloading --> {org_link}')
    download(url, img_nr)

Output:
E:\div_code\home
λ python roman.py
Dowloading --> https://swordscomic.com/comic/CCCLXI/

CCCLXI.png
[Image: I58IDh.png]
roman_convert that i import is not written bye me,just code from first hit on Google.

Hide/Show

# roman_convert.py
def roman_to_int(s):
    rom_val = {'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}
    int_val = 0
    for i in range(len(s)):
        if i > 0 and rom_val[s[i]] > rom_val[s[i - 1]]:
            int_val += rom_val[s[i]] - 2 * rom_val[s[i - 1]]
        else:
            int_val += rom_val[s[i]]
    return int_val

def int_to_roman(num):
        val = [
            1000, 900, 500, 400,
            100, 90, 50, 40,
            10, 9, 5, 4,
            1
            ]
        syb = [
            "M", "CM", "D", "CD",
            "C", "XC", "L", "XL",
            "X", "IX", "V", "IV",
            "I"
            ]
        roman_num = ''
        i = 0
        while  num > 0:
            for _ in range(num // val[i]):
                roman_num += syb[i]
                num -= val[i]
            i += 1
        return roman_num
if __name__ == '__main__':
    n = int_to_roman(362)
    print(n) # CCCLXII
    print(roman_to_int(n)) # 362

[Brompy]

Thank you both for the replies.

Snippsat, your solution is very cool/clever. But when I try to use it does download a .png, but it is an unreadable .png file that is only 13kb large. What is going wrong?

[snippsat]

But when I try to use it does download a .png, but it is an unreadable .png file that is only 13kb large. What is going wrong?

Not all days have images,so it will be 13kb on these days.
Setup is:

E:\div_code\home\
  |-- roman.py
  |-- roman_convert

If i change roman.py to download more images at once.
Also make it so it show days with no image in both int and roman numb.
So here download 25 days,4 days has no image as show in list under.

[('CCCXLVI.png', 346), ('CCCXLVII.png', 347), ('CCCLVI.png', 356), ('CCCLXIII.png', 363)]

# roman.py
import requests
import os, re
from roman_convert import roman_to_int, int_to_roman

def make_url(roman_number):
    return f'https://swordscomic.com/comic/{roman_number}/'

no_image = []
def download(url, img_nr):
    img = requests.get(url)
    img_name = f'{int_to_roman(img_nr)}.png'
    with open(img_name, 'wb') as f_out:
        if len(img.content) < 15000:
            no_image.append(img_name)
        else:
            f_out.write(img.content)

if __name__ == '__main__':
    #img_nr = 364
    for img_nr in range(340, 365):
        url = f'https://swordscomic.com/media/Swords{img_nr}t.png'
        roman_number = int_to_roman(img_nr)
        org_link = make_url(roman_number)
        print(f'Dowloading --> {org_link}')
        download(url, img_nr)
    day_int = [roman_to_int(ro.split('.')[0]) for ro in no_image]
    print(list(zip(no_image, day_int)))

Run:

Output:
E:\div_code\home
λ python roman.py
Dowloading --> https://swordscomic.com/comic/CCCXL/
Dowloading --> https://swordscomic.com/comic/CCCXLI/
Dowloading --> https://swordscomic.com/comic/CCCXLII/
Dowloading --> https://swordscomic.com/comic/CCCXLIII/
Dowloading --> https://swordscomic.com/comic/CCCXLIV/
Dowloading --> https://swordscomic.com/comic/CCCXLV/
Dowloading --> https://swordscomic.com/comic/CCCXLVI/
Dowloading --> https://swordscomic.com/comic/CCCXLVII/
Dowloading --> https://swordscomic.com/comic/CCCXLVIII/
Dowloading --> https://swordscomic.com/comic/CCCXLIX/
Dowloading --> https://swordscomic.com/comic/CCCL/
Dowloading --> https://swordscomic.com/comic/CCCLI/
Dowloading --> https://swordscomic.com/comic/CCCLII/
Dowloading --> https://swordscomic.com/comic/CCCLIII/
Dowloading --> https://swordscomic.com/comic/CCCLIV/
Dowloading --> https://swordscomic.com/comic/CCCLV/
Dowloading --> https://swordscomic.com/comic/CCCLVI/
Dowloading --> https://swordscomic.com/comic/CCCLVII/
Dowloading --> https://swordscomic.com/comic/CCCLVIII/
Dowloading --> https://swordscomic.com/comic/CCCLIX/
Dowloading --> https://swordscomic.com/comic/CCCLX/
Dowloading --> https://swordscomic.com/comic/CCCLXI/
Dowloading --> https://swordscomic.com/comic/CCCLXII/
Dowloading --> https://swordscomic.com/comic/CCCLXIII/
Dowloading --> https://swordscomic.com/comic/CCCLXIV/
[('CCCXLVI.png', 346), ('CCCXLVII.png', 347), ('CCCLVI.png', 356), ('CCCLXIII.png', 363)] 

---

Can show a quick test with Selenium,as this is maybe not so easy if new to this.
Here i go back 3 times,then send site source code to BS,so can to find the real download(it's not the roman numerals link) link in meta tag.
To download i use same function with some modifications.

from selenium import webdriver
from selenium.webdriver.chrome.options import Options
from selenium.webdriver.common.keys import Keys
from bs4 import BeautifulSoup
import time, os
import requests

def download(img_url):
    img = requests.get(img_url)
    img_name = os.path.basename(img_url)
    with open(img_name, 'wb') as f_out:
        if len(img.content) < 15000:
            no_image.append(img_name)
        else:
            f_out.write(img.content)

if __name__ == '__main__':
    #--| Setup
    chrome_options = Options()
    #chrome_options.add_argument("--headless")
    browser = webdriver.Chrome(executable_path=r'C:\cmder\bin\chromedriver.exe')

    #--| Parse or automation
    browser.get('https://swordscomic.com/comic/CCCLXV/')
    back = browser.find_elements_by_css_selector('#navigation-previous')[0].click()
    time.sleep(3)
    back = browser.find_elements_by_css_selector('#navigation-previous')[0].click()
    time.sleep(3)
    back = browser.find_elements_by_css_selector('#navigation-previous')[0].click()

    # Give source code to BeautifulSoup
    soup = BeautifulSoup(browser.page_source, 'html.parser')
    img_url = soup.find('meta', property="og:image")
    img_url = img_url.attrs['content']
    download(img_url)
    browser.quit()