CODEWITHSUNDEEP
templatesjinja2
Christian
Christian

Reputation: 1166

How to get a list of current variables from Jinja 2 template?

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?

Upvotes: 32

Views: 29907

Answers (4)

Jamie
Jamie

Reputation: 329

Jinja2 now has an extension that will give you debug information. Example using Flask:

import flask

app = flask.Flask(__name__)
app.jinja_env.add_extension('jinja2.ext.debug')

@app.route('/')
def hello():
    return flask.render_template('hello.html')

DEBUG = True # Or from your environment settings
if DEBUG:
    print("Running in DEBUG mode.")

@app.context_processor
def commonContext():
    context = {"DEBUG":DEBUG} # And any other variables you always want every template to be able to see
    return context

if __name__ == '__main__':
    app.run(debug=DEBUG)

At the bottom of your hello.html (or in your base template):

{% if DEBUG %}
<section>
  <h3>Debug Info</h3>
  <pre>{% debug %}</pre>
</section>
{% endif %}

Upvotes: 0

Jo Sprague
Jo Sprague

Reputation: 17353

I found @Garrett's answer to be a bit more complex than what I wanted. I found that I can easily inspect the context by adding a clone of the context to the context itself:

contextCopy = dict(context)
context['all'] = contextCopy

And then pretty printing that into my Jinja template with <pre>{{ all|pprint }}</pre>.

Upvotes: 3

Garrett
Garrett

Reputation: 49768

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.]

Upvotes: 39

joemaller
joemaller

Reputation: 20556

Here's how to get @crewbum's answer working from a Flask app:

import jinja2

@jinja2.contextfunction
def get_context(c):
    return c

app.jinja_env.globals['context'] = get_context
app.jinja_env.globals['callable'] = callable

Upvotes: 4

Related Questions