In the ISBN-13 system, each book is assigned a unique 13-digit code. The first twelve digits identify the book itself, whereas the last digit merely serves as a check digit to detect invalid ISBN-13 codes.

If $$x_1, \ldots, x_{12}$$ represent the first twelve digits of an ISBN-13 code, the check digit $$x_{13}$$ is computed as \[\begin{align} o &= x_1 + x_3 + x_5 + x_7 + x_9 + x_{11} \\ e &= x_2 + x_4 + x_6 + x_8 + x_{10} + x_{12} \\ x_{13} &= (10 - (o + 3e)\!\!\!\!\mod{10})\!\!\!\!\mod{10}\end{align}\] As a result, the check digit $$x_{13}$$ always takes a value in between 0 and 9, so that ISBN-13 codes only contain digits.

The website ISBNdb.com¹ is a database of books. It provides a so-called Application Programming Interface² (API) that allows computer programs to retrieve information about a particular book through its ISBN-13 code. We simulated this API for the purpose of this assignments (because the original API has become a paid service). For example, if you open the URL

https://pythia.ugent.be/pythia-share/exercises/isbn9/books.php?isbn=97801361106753

a file will be downloaded with the following content

<?xml version="1.0" encoding="UTF-8"?>

<ISBNdb server_time="2012-11-19T07:28:26Z">
<BookList total_results="1" page_size="10" page_number="1" shown_results="1">
<BookData book_id="the_practice_of_computing_using_python" isbn="0136110673" isbn13="9780136110675">
<Title>The Practice of Computing using Python</Title>
<TitleLong></TitleLong>
<AuthorsText>William F Punch, Richard Enbody, </AuthorsText>
<PublisherText publisher_id="addison_wesley_a01">Addison Wesley</PublisherText>
</BookData>
</BookList>
</ISBNdb>

This is a file in XML format⁴. It contains a lot of information about the book, but for this assignment we are only interested in its title, authors and publishers. The most important part of the URL

https://pythia.ugent.be/pythia-share/exercises/isbn9/books.php?isbn=97801361106755

is the part highlighted in red. At this location, you have to insert the ISBN-13 code of the book you wish to lookup information for.

Assignment

Write a function display_book_info that takes an ISBN-13 code (str). If the given ISBN-13 code is valid, the function must print the title, the authors and the publishers in the format you can derive from the example below. If the given ISBN-13 code is invalid, and error message must be printed as in the example below.

Example

>>> display_book_info('9780136110675')
Title: The Practice of Computing using Python
Authors: William F Punch, Richard Enbody
Publisher: Addison Wesley
>>> display_book_info('9780136110678')
Wrong ISBN-13 code