Why is this not working? [Django]

Question

I am struggling with this

{% extends "base_generic.html" %}
{% block content %}        
<h1>{{ author.first_name }} {{ author.last_name }}</h1>
{% for book in view.books_by_author %}
    {% if author.last_name  in book.author %}
        <p>{{ book.title }}</p>       
    {% endif %}
{% endfor %}    
{% endblock %}

"author" is a context variable. This is books_by_author function:

def books_by_author(self): 
    books = Book.objects.all()  
    return books

This portion is not working:

{% if author.last_name  in book.author %}
        <p>{{ book.title }}</p>

But when I tried this, it's working. Is there a way to make "book.author" a string or is there a way around?

{% if "Twain"  in book.author %}
        <p>{{ book.title }}</p>

Answer 1

You should compare with the last_name of the related author

{% if author.last_name in book.author.last_name %}
    <p>{{ book.title }}</p>       
{% endif %}

Or more strictly, use ==:

{% if author.last_name == book.author.last_name %}
    <p>{{ book.title }}</p>       
{% endif %}