Question

If I return a Jinja2 template like so:
return render_response('home.htm', **context)

How do then get a list of the variables in context from within the template?

Answer 1

Technically, because context is not passed as a named dictionary, a little work is required to generate a list of the context variables from inside a template. It is possible though.

1. Define a Jinja context function to return the jinja2.Context object, which is essentially a dictionary of the global variables/functions

2. Make that function available in the global namespace; i.e. a jinja2.Environment or jinja2.Template globals dictionary

3. Optionally, filter objects from the context; for instance, use callable() to skip Jinja’s default global helper functions (range, joiner, etc.). This may be done in the context function or the template; wherever it makes the most sense.

Example:

>>> import jinja2
>>> 
>>> @jinja2.contextfunction
... def get_context(c):
...         return c
... 
>>> tmpl = """ 
... {% for key, value in context().items() %}
...     {% if not callable(value) %}
...         {{ key }}:{{ value }}
...     {% endif %}
... {% endfor %}
... """
>>> 
>>> template = jinja2.Template(tmpl)
>>> template.globals['context'] = get_context
>>> template.globals['callable'] = callable
>>>
>>> context = {'a': 1, 'b': 2, 'c': 3}
>>> 
>>> print(template.render(**context))
        a:1
        c:3
        b:2

[Alternately, call render_response with ('home.htm', context=context) to make the other solution work.]