How to use a function with jinja2

Question

In a .py file I have a function that creates a tree with information (name, type, size etc), given a ziped file. (I want to create a tree view of this ziped file) There is another function that generates <ul> and <li> tags for the name of the components, nested if there are children. The function doesn't return anything.

What I want is to have a block in the jinja template displaying the html code from the above function.

The function is:

def print_tree(tree):
    print "<ul>"
    for t in tree:
        print "<li>" + t['name']
        if 'children' in t:
            print_tree(t['children'])
        print "</li>"
    print "</ul>"

How can I do this?

Answer 1

Have your function return a string, not print:

def print_tree(tree):
    result = ['<ul>']
    for t in tree:
        result.append("<li>" + t['name'])
        if 'children' in t:
            result.append(print_tree(t['children']))
        result.append("</li>")
    result.append("</ul>")
    return '\n'.join(result)

You can do the same thing directly in Jinja without a function:

<ul>
{%- for t in tree recursive %}
    <li>{{ t.name }}
    {%- if t.children -%}
        <ul>{{ loop(t.children) }}</ul>
    {%- endif %}</li>
{%- endfor %}
</ul>

Here the loop() call will reuse the for loop marked recursive producing a recursive tree structure the same way the print_tree() function does.