Lists and dictionaries

Django's template context is a dict mapping names to values. Querysets behave like lazy lists. JSON APIs serialize dicts. Mastering collections is essential.

Dictionaries as context

context = {
    "articles": Article.objects.filter(published=True),
    "page_title": "Blog home",
}

Templates access keys: {{ page_title }}, {% for article in articles %}.

Lists and querysets

Querysets support filtering, slicing, and ordering—similar to chaining list operations but executed as SQL. list(queryset) forces evaluation when you need a concrete list.

Important interview questions and answers

1. Q: Dict vs model instance in templates?
   A: Models expose attributes (article.title); dicts use keys—both work in Django templates.
2. Q: When is a queryset evaluated?
   A: On iteration, slicing, len(), list(), or printing—until then it is lazy SQL.
3. Q: Mutable default dict pitfall?
   A: Never use def f(x={})—shared mutable defaults cause bugs; Django model field defaults use callables like dict or list correctly via default=list.

Self-check

1. What is a view's context dict for?
2. When does a queryset hit the database?