Obtain context from within Django custom template filter

getContext.py

"""
What if you suddenly need to have access to the context object from within
certain filters, and it would be costly to alter its syntax?  Well, that 
just happend to me.  Here is my solution.
"""

def get_context(max_depth=4):
    """A simple (and perhaps dangerous) way of obtaining a context.  Keep
    in mind these shortcomings:
        1.  There is no guarantee this returns the right 'context'.
        2.  This only works during render execution.  So, be sure your 
        filter continues to work in other cases.
    
    This approach uses the 'inspect' standard Python Library to harvest
    the context from the call stack.
    """
    import inspect
    stack = inspect.stack()[2:max_depth]
    context = {}
    for frame_info in stack:
        frame = frame_info[0]
        arg_info = inspect.getargvalues(frame)
        if 'context' in arg_info.locals:
            context = arg_info.locals['context']
            break
    return context

#Example of useage
@register.filter(name='distance')
def distance(locatable, locatable2=None):
    """
    Output nice distance information
    """
    log.debug('distance filter')
    
    context = get_context()
    if context:
        value = context['my_important_context_value'] # <<< this could be 'request'
        log.debug('This came from the context: %s', value)
    
    from support.geotools import Point
    if not locatable2:
        locatable2 = getattr(locatable, 'nearest_major_city_or_town', None)
    if not locatable2:
        return ''
    
    try:
        p1 = Point(locatable)
        p2 = Point(locatable2)
    
        if p1 and p2:
            return p1 - p2
    except:
        pass
    return ''