pass a constant value to all templates django code example

Example: how to get all template project in settinge use django

BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
PROJECT_DIR = os.path.dirname(os.path.abspath(__file__))

class InvalidTemplateVariable(str):
    def __mod__(self,other):
        from django.template.base import TemplateSyntaxError
        raise TemplateSyntaxError("Invalid variable : '%s'" % other)

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': ['%s/templates/' % (PROJECT_DIR),'%s/dev_templates/' % (PROJECT_DIR),],
        'APP_DIRS': True,
        'OPTIONS': {
            'string_if_invalid': InvalidTemplateVariable("%s"),
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]