What is length in matrix.html?

Question

I was going through this solution of pset6 (more comfortable) and I fail to understand the following for loop:

{% for i in range((s2)|length + 1) %}
            <th>{{i}}</th>
{% endfor %}

Specifically, I want to know, what is length, from where are we getting it and why does removing it gives an internal server error.

Answer 1

Since it's in a jinja "statment", maybe it's a jinja thing. An internet search for 'jinja length' finds this:

length(object)

Return the number of items of a sequence or mapping.
Aliases: count

There are a lot of other results you may find interesting.

Answer 2

Jinja, unfortunately, does not support executing arbitrary Python code, such as

len(s2)

Hence, in order to get the length of a string, the use of a filter is required.