Django template and the locals trick

Question

The django books gives the local trick in order to avoid to type a long list of parameters as context dictionnary

http://www.djangobook.com/en/2.0/chapter04/

Answer 1

To reduce clutter in views.py while keeping things explicit: In controllers.py:

import sys

def auto_context(the_locals=None):
    # Take any variable in the locals() whose name ends with an underscore, and
    # put it in a dictionary with the underscore removed.

    if the_locals is None:
        # We can access the locals of the caller function even if they
        # aren't passed in.
        caller = sys._getframe(1)
        the_locals = caller.f_locals

    return dict([
        (key[:-1], value)
        for (key, value) in the_locals.items()
        if key[-1] == "_"])

In views.py:

from app.controllers import auto_context

def a_view(request): 
    hello_ = "World" # This will go into the context.
    goodnight = "Moon" # This won't.
    return render(request, "template.html", auto_context())

In template.html, use {{ hello }}.

You're unlikely to give a variable a name ending in an underscore accidentally. So you'll know exactly what's going into the template. Use auto_context() or equivalently auto_context(locals()). Enjoy!