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     Antipatterns

    1. A GET request with side-effects
    2. A model with a …Model suffix
    3. calling all() before count() or filter() etc.
    4. Chaining querysets together
    5. Checking if an object is created with instance.pk
    6. Checking ownership through the UserPassesTestMixin
    7. Checking request method with if request.POST
    8. Constructing a new form when validation fails
    9. Data duplication
    10. Fetching the logged in user with a query
    11. Fill the primary key gaps
    12. Filter on arbitrary input like request.GET
    13. Filtering in the template
    14. Foreign key with _id suffix
    15. Giving related_name=… the same name as the relation
    16. Imports
    17. Manually constructing a slug
    18. Modifying slugs and primary keys of model objects
    19. non-atomic JSONFields
    20. (Over)use of .values()
    21. passing function references to reverse
    22. Passing parameters directly in the query string of a URL
    23. Plural model class names
    24. Processing request data manually
    25. Refer to the User model directly
    26. Rendering content after a successful POST request
    27. Rendering into JavaScript
    28. Return a JsonResponse with safe=False
    29. Run makemigrations in production
    30. Signals
    31. Use datetime.now as default=… for a created_on field
    32. Use .get(…) to retrieve the object in a view
    33. Users controlling a primary key
    34. Using a FloatField for currencies
    35. Using commit=False when altering the instance in a ModelForm
    36. Using len(…) on a QuerySet with no further use
    37. Using multiple forms on the same page without prefixing
    38. Using regular HTML comments instead of Django template comments
    39. Using request.POST or None

     Patterns

    1. A default record per entity
    2. A field that is derived from another field
    3. A SET(…) delete handler with the object as parameter
    4. Annotate a condition as BooleanField
    5. Date(Time)Fields that store a week or month
    6. Dictionary lookups for the database
    7. Match multiple strings in a case-insensitive manner
    8. querying in the opposite direction
    9. Set values to a created/updated object in a class-based view

     Difference between …

    1. ForeignKey and OneToOneField
    2. reverse and redirect

     Troubleshooting

    1. A certain field does not appear in the migrations and in the database table
    2. Can not extract/filter a Date(Time)Field when time zones are enabled

     QA

    1. How do calls of models.Manager and custom managers work?