What is the best option to replace a loop?
according to the query, it seems that the row count is either 0 or 1. so the loop would either have no iterations (the else part) or have exactly one iteration.
in terms of performance, I think that any improvement here is not dramatic.
however, in terms of choosing the right coding tools for the job, it seems that a loop is not the right tool.
maybe the following would be better:
@app.route(&quot;/&quot;)
@login_required
def index():
    &quot;&quot;&quot;Queries the user's First Name to display in the title&quot;&quot;&quot;
    names = db.execute(&quot;&quot;&quot;
        SELECT first_name
        FROM users
        WHERE id=:user_id
        &quot;&quot;&quot;,
        user_id = session[&quot;user_id&quot;]    
    )
    first_name = names[0][&quot;first_name&quot;] if names else None
    return render_template(&quot;index.html&quot;, first_name = first_name)

and then:
&lt;header class=&quot;mainHeader&quot;&gt;
  {% if first_name %}
    &lt;h1&gt;{{ first_name }}'s Bookshelf&lt;/h1&gt;
  {% else %}
    &lt;h1&gt;Your Bookshelf&lt;/h1&gt;
  {% endif %}
&lt;/header&gt;

note: I didn't test the code.