randpage.py: Display a random page from a random PDF

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Blog 2019/11/27

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randpage.py: Display a random page from a random PDF

2025/4/3 updates: use python3, use set -e, combine cmdline util + webapp into unified script.

Here's a Python script which will display a random page from a random PDF (in the current directory).

It's a fun way to encourage you to pick up one of your books which has been (digitally) collecting dust.

You can run it as a command-line utility (which will open the random page in Preview.app), or pass the --serve flag to run it as a Flask webapp on localhost:8000.

Assumptions:

• macOS
• pdftk (brew install pdftk-java)
• pdfinfo (brew install xpdf)
• exiftool (brew install exiftool)

randpage.py

#!/usr/bin/env python3

# randpage.py: display a random page from a directory of pdf files.
# Copyright 2019 Jason Pepas
# Released under the terms of the MIT license, see https://opensource.org/license/mit

# Usage:
#   Open a random page using Preview.app:
#     $ ./randpage.py
#   Run as a webapp on localhost:8000:
#     $ ./randpage.py --serve

import sys
import os
import random
import subprocess


def check_deps():
    "check if we have all of the dependencies installed"
    if os.system("which -s pdfinfo") != 0:
        sys.stderr.write("Error: pdfinfo not installed.\n")
        sys.stderr.write("Try 'brew install xpdf'.\n")
        sys.exit(1)
    if os.system("which -s pdftk") != 0:
        sys.stderr.write("Error: pdftk not installed.\n")
        sys.stderr.write("Try 'brew install pdftk-java'.\n")
        sys.exit(1)
    if os.system("which -s exiftool") != 0:
        sys.stderr.write("Error: exiftool not installed.\n")
        sys.stderr.write("Try 'brew install exiftool'.\n")
        sys.exit(1)


def random_book(path):
    "return a random book among the books in the current directory."
    books = [fname for fname in os.listdir(path) if fname.endswith('.pdf')]
    return random.choice(books)


def page_count(fname):
    "return the page count of the given book."
    cmd = "set -e -o pipefail; pdfinfo \"%s\" | grep Pages: | awk '{print $2}'" % fname
    output = subprocess.check_output(cmd, shell=True)
    return int(output)


def pluck_page(book_fname, pagenum):
    "extract the given page from the given book."
    cmd = "set -e; pdftk \"%s\" cat %s output /tmp/random-page.pdf" % (book_fname, pagenum)
    subprocess.check_call(cmd, shell=True)
    # set the metadata title of the pdf to indicate the book title and page number.
    title = "%s, page %s" % (book_fname.split('/')[-1], pagenum)
    cmd = "set -e; exiftool -Title=\"%s\" /tmp/random-page.pdf" % title
    subprocess.check_call(cmd, shell=True)
    return "/tmp/random-page.pdf"


def display_page(fname):
    "display the extracted book page."
    subprocess.check_call("set -e; open %s" % fname, shell=True)


def display_random_page(books_path):
    "display a random page from a random book."
    book_fname = random_book(books_path)
    pages = page_count(book_fname)
    pagenum = random.randrange(pages) + 1
    print("%s, page %s of %s" % (book_fname, pagenum, pages))
    page_fname = pluck_page(book_fname, pagenum)
    display_page(page_fname)


def serve(books_path):
    "run as a webapp on port 8000."
    import flask
    application = flask.Flask(__name__)

    @application.route("/")
    def GET_root(methods=['GET']):
        book_fname = random_book(books_path)
        pages = page_count(books_path + book_fname)
        pagenum = random.randrange(pages) + 1
        page_fname = pluck_page(books_path + book_fname, pagenum)
        with open(page_fname, 'rb') as f:
            pdf = f.read()
        response = flask.make_response(pdf)
        response.headers['Content-Type'] = 'application/pdf'
        response.headers['Content-Disposition'] = \
            'inline; filename=%s' % book_fname
        response.headers["x-filename"] = book_fname
        response.headers["Access-Control-Expose-Headers"] = 'x-filename'
        return response

    application.run('0.0.0.0', port=8000, debug=False)


if __name__ == "__main__":
    check_deps()
    books_path = './'
    if '--serve' in sys.argv:
        serve(books_path)
    else:
        display_random_page(books_path)