Overriding Variables of Outer Scopes

[MrOrz]

In Jinja 1.2 there was a feature that allows us to override outer scope variables from within a inner scope, by adding an exclamation mark after the set statement.

This feature is somehow missing in Jinja2. However, such feature is often required. Here is a real-world example in stackoverflow:
http://stackoverflow.com/questions/4870346/can-a-jinja-variables-scope-extend-beyond-in-an-inner-block

It would be glad to see such feature back again in Jinja2 ; )

[mitsuhiko]

I will keep it in mind for the new compiler backend, but in the current one that is not possible to achieve for performance reasons.

[medwards]

I'd like to see this too.

[palmkevin]

+1

[smatthews1999]

I would like to see this too.

I'm trying to perform simple running totals in some generated data..and that functionality is what I need.

[smeggingsmegger]

+1

[alexcasalboni]

+1

[ruiposse]

+1

I also think that this behaviour should be unacceptable:

{% set first_run = True %} {% for i in range(3) %}
{% for j in range(3) %} {% if first_run %} {% set first_run = False %}
• {{ i }}, {{ j }}
{% endif %} {% endfor %}
{% endfor %}

This will output 3

tags, but it should output only one.
The variable resets after each outer loop run, even though it was declared OUTSIDE of all loops.

I can't see how this would be expected behaviour. Is this a bug ?

[ruiposse]

+1

I also think that this behaviour should be unacceptable:

<ul>
  {% set first_run = True %}
  {% for i in range(3) %}
  <ul>
    {% for j in range(3) %}
    {% if first_run %}
    {% set first_run = False %}
    <li>{{ i }}, {{ j }}</li>
    {% endif %}
    {% endfor %}
  </ul>
  {% endfor %}
</ul>

This will output 3 <li> tags, but it should output only one.

The variable resets after each outer loop run, even though it was declared OUTSIDE of all loops.
I can't see how this would be expected behaviour. Is this a bug ?

[skuda]

+1

[thaddeusmt]

This would very useful when templating JSON files. +1

[dpgaspar]

+1

[dlenski]

Me too, could really use an override and it'd be great if the template designer docs explicitly mentioned this behavior!

I had to work with some data in an (admittedly horrible) format and was puzzled at why the followed pre-pass didn't work...

{% set last_one = none %}
{% for row in rows %}
    {% set last_one = row.field %}
{% endfor %}

I agree with @ruiposse's comment that having a variable first set outside all loops reset itself inside them is very unexpected.

[t2y]

+1

[mitsuhiko]

I'm going to close this. This cannot work in all cases in Jinja2 and I do not really wish on supporting it.