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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. Fetching the logged in user with a query
    10. Fill the primary key gaps
    11. Filter on arbitrary input like request.GET
    12. Filtering in the template
    13. Foreign key with _id suffix
    14. Giving related_name=… the same name as the relation
    15. Imports
    16. Manually constructing a slug
    17. Modifying slugs and primary keys of model objects
    18. non-atomic JSONFields
    19. (Over)use of .values()
    20. passing function references to reverse
    21. Passing parameters directly in the query string of a URL
    22. Plural model class names
    23. Processing request data manually
    24. Refer to the User model directly
    25. Rendering content after a successful POST request
    26. Rendering into JavaScript
    27. Return a JsonResponse with safe=False
    28. Run makemigrations in production
    29. Signals
    30. Use datetime.now as default=… for a created_on field
    31. Use .get(…) to retrieve the object in a view
    32. Users controlling a primary key
    33. Using a FloatField for currencies
    34. Using commit=False when altering the instance in a ModelForm
    35. Using len(…) on a QuerySet with no further use
    36. Using multiple forms on the same page without prefixing
    37. Using regular HTML comments instead of Django template comments
    38. 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?