Get the average number of pages of your books on a given Goodreads shelf

goodreads_shelf_average_page_number.py

#!/usr/bin/python3

"""
This script returns the average number of pages of the books on a given Goodreads shelf.
Example Output:
> $ python3 goodreads_shelf_average_page_number.py                                                                    
Average page number: 354
Number of books in shelf to-read-next with known page numbers: 19/24
Total number of pages in your shelf: 8496
To read that within one year, you need to read 23 pages a day

Usage:
- Edit the three variables below (user, shelf, key)
- Get API Developer Key here (only couple of clicks): https://www.goodreads.com/api/keys
- User ID can be retrieved from the URL of your Goodreads profile
- Make your profile temporarily public: https://www.goodreads.com/user/edit
- Run the script with python >= 3.6
"""

from functools import reduce

import requests
from lxml import etree

USER_ID = '' # something like '54988141'. Profile needs to be public!
SHELF = 'to-read-next'
DEVELOPER_KEY = ''

url = f'https://www.goodreads.com/review/list/{USER_ID}.xml?key={DEVELOPER_KEY}&v=2&shelf={SHELF}&per_page=200&page=1'
# print(f'Querying ... ({url})')
xml_string = requests.get(url).content

root = etree.fromstring(xml_string)

pages_list = []
for review in root.find('reviews'):
	book = review.find('book')
	pages = book.find('num_pages').text
	if pages is not None:
		pages_list.append(int(pages))

averge_page_number = reduce(lambda x, y: x + y, pages_list) // len(pages_list)
number_of_books_in_shelf = len(root.find('reviews').getchildren())
total_number_of_pages_in_shelf = averge_page_number * number_of_books_in_shelf
print(f'Average page number: {averge_page_number}')
print(f'Number of books in shelf {SHELF} with known page numbers: {len(pages_list)}/{number_of_books_in_shelf}')
print(f'Total number of pages in your shelf: {total_number_of_pages_in_shelf}')
print(f'To read that within one year, you need to read {total_number_of_pages_in_shelf // 365} pages a day')