from django import template
register = template.Library()
@register.simple_tag(takes_context=True)
def url_replace(context, field, value):
    request = context['request']
    dict_ = request.GET.copy()
    dict_[field] = value
    return dict_.urlencode()

@register.inclusion_tag("shop/elements/test.html", takes_context=True)
def draw_test(context):
	print dir(context)

['__class__', '__contains__', '__copy__', '__delattr__', '__delitem__', '__dict__', '__doc__', '__eq__', '__format__', '__getattribute__', '__getitem__', '__hash__', '__init__', '__iter__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', '_current_app', '_reset_dicts', 'autoescape', 'bind_template', 'current_app', 'dicts', 'flatten', 'get', 'has_key', 'is_current_app_set', 'new', 'pop', 'push', 'render_context', 'setdefault', 'template', 'template_name', 'update', 'use_l10n', 'use_tz']