Can a Jinja variable's scope extend beyond in an inner block?

One way around this limitation is to enable the "do" expression-statement extension and use an array instead of boolean:

{% set exists = [] %}
{% for i in range(5) %}
      {% if True %}
          {% do exists.append(1) %}
      {% endif %}
{% endfor %}
{% if exists %}
    <!-- exists is true -->
{% endif %}

To enable Jinja's "do" expression-statement extension: e = jinja2.Environment(extensions=["jinja2.ext.do",])

Answer to a related question: I wanted to have a global counter of the number of times I entered a certain if-block in the template, and ended up with the below.

At the top of the template:

{% set counter = ['1'] %}

In the if-block I want to count:

{% if counter.append('1') %}{% endif %}

When displaying the count:

{{ counter|length }}

The string '1' can be replaced with any string or digit, I believe. It is still a hack, but not a very large one.

Update 2018

As of Jinja 2.10 (8th Nov 2017) there is a namespace() object to address this particular problem. See the official Assignments documentation for more details and an example; the class documentation then illustrates how to assign several values to a namespace.