[FIXED] Flask: Jinja for loop works only once per template

Issue

I have a Flask app and I am using a for loop to generate html dynamically:

    {% for subcategory in subcategories|unique: %}
List of projects:
        <p> {{ subcategory }}</p>
        {% endfor %}


    {% for subcategory in subcategories|unique: %}
List of subcategories:
       <p> {{ subcategory }}</p>
        {% endfor %}

However, the second for loop does not produce anything.

If I delete the "|unique" then it works.

Why?

Solution

You may be passing in a generator as opposed to a list or other iterable object.

An example generator might be:

subcategories = [str(item) for item in subcategories]

On the Python end, try wrapping the item in a list before sending it over to the Jinja renderer:

subcategories = list([str(item) for item in subcategories])

Answered By - Daniel Bond