How to properly use the choices field option in Django

Question

I m reading the tutorial here  https   docs djangoproject com en 1 5 ref models fields  choices and i m trying to create a box where the user can select the month he was born in  What I tried was   MONTH CHOICES          JANUARY   January         FEBRUARY   February         MARCH   March                  DECEMBER   December       month   CharField max length 9                    choices MONTHS CHOICES                    default JANUARY    Is this correct  I see that in the tutorial I was reading  they for some reason created variables first  like so  FRESHMAN    FR  SOPHOMORE    SO  JUNIOR    JR  SENIOR    SR    Why did they create those variables  Also  the MONTHS CHOICES is in a model called People  so would the code I provided create a  Months Choices  column in the database called called  People  and would it say what month the user was born in after he clicks on of the months and submits the form

User · Answer

The cleanest solution is to use the django-model-utils library   from model utils import Choices  class Article models Model       STATUS   Choices  draft    published       status   models CharField choices STATUS  default STATUS draft  max length 20    https   django-model-utils readthedocs io en latest utilities html choices

User · Answer

You can t have bare words in the code  that s the reason why they created variables  your code will fail with NameError    The code you provided would create a database table named month  plus whatever prefix django adds to that   because that s the name of the CharField   But there are better ways to create the particular choices you want  See a previous Stack Overflow question   import calendar tuple  m  m  for m in calendar month name 1

User · Answer

According to the documentation      Field choices       An iterable  e g   a list or tuple  consisting itself of   iterables of exactly two items  e g    A  B    A  B        to use as   choices for this field  If this is given  the default form widget will   be a select box with these choices instead of the standard text field       The first element in each tuple is the actual value to be stored  and   the second element is the human-readable name    So  your code is correct  except that you should either define variables JANUARY  FEBRUARY etc  or use calendar module to define MONTH CHOICES   import calendar      class MyModel models Model                MONTH CHOICES     str i   calendar month name i   for i in range 1 13        month   models CharField max length 9  choices MONTH CHOICES  default  1

User · Answer

I think no one actually has answered to the first question      Why did they create those variables    Those variables aren t strictly necessary  It s true  You can perfectly do something like this   MONTH CHOICES           JANUARY    January          FEBRUARY    February          MARCH    March                     DECEMBER    December       month   models CharField max length 9                    choices MONTH CHOICES                    default  JANUARY     Why using variables is better  Error prevention and logic separation   JAN    JANUARY  FEB    FEBRUARY  MAR    MAR           MONTH CHOICES          JAN   January         FEB   February         MAR   March                    DEC   December        Now  imagine you have a view where you create a new Model instance  Instead of doing this   new instance   MyModel month  JANUARY     You ll do this   new instance   MyModel month MyModel JAN    In the first option you are hardcoding the value  If there is a set of values you can input  you should limit those options when coding  Also  if you eventually need to change the code at the Model layer  now you don t need to make any change in the Views layer

User · Answer

I would suggest to use django-model-utils instead of Django built-in solution   The main advantage of this solution is the lack of string declaration duplication  All choice items are declared exactly once  Also this is the easiest way for declaring choices using 3 values and storing database value different than usage in source code   from django utils translation import ugettext lazy as   from model utils import Choices  class MyModel models Model      MONTH   Choices           JAN      January              FEB      February              MAR      March                       month   models CharField         max length 3         choices MONTH         default MONTH JAN         And with usage IntegerField instead   from django utils translation import ugettext lazy as   from model utils import Choices  class MyModel models Model      MONTH   Choices          1   JAN      January             2   FEB      February             3   MAR      March                       month   models PositiveSmallIntegerField         choices MONTH         default MONTH JAN          This method has one small disadvantage  in any IDE  eg  PyCharm  there will be no code completion for available choices  it   s because those values aren   t standard members of Choices class

User · Answer

pip install django-better-choices For those who are interested  I have created django-better-choices library  that provides a nice interface to work with Django choices for Python 3 7   It supports custom parameters  lots of useful features and is very IDE friendly  You can define your choices as a class  from django better choices import Choices   class PAGE STATUS Choices       CREATED    Created      PENDING   Choices Value  Pending   help text  This set status to pending       ON HOLD   Choices Value  On Hold   value  custom on hold        VALID   Choices Subset  CREATED    ON HOLD        class INTERNAL STATUS Choices           REVIEW    On Review        classmethod     def get help text cls           return tuple              value help text             for value in cls values               if hasattr value   help text              Then do the following operations and much much more  print  PAGE STATUS CREATED                     created  print  PAGE STATUS ON HOLD                     custom on hold  print  PAGE STATUS PENDING display             Pending  print  PAGE STATUS PENDING help text           This set status to pending    custom on hold  in PAGE STATUS VALID         True PAGE STATUS CREATED in PAGE STATUS VALID      True  PAGE STATUS extract  CREATED    ON HOLD          PAGE STATUS VALID  for value  display in PAGE STATUS      print  value  display    PAGE STATUS get help text   PAGE STATUS VALID get help text    And of course  it is fully supported by Django and Django Migrations  class Page models Model       status   models CharField choices PAGE STATUS  default PAGE STATUS CREATED   Full documentation here  https   pypi org project django-better-choices

User · Answer

For Django3 0   use models TextChoices  see docs-v3 0 for enumeration types  from django db import models  class MyModel models Model       class Month models TextChoices           JAN    1    quot JANUARY quot          FEB    2    quot FEBRUARY quot          MAR    3    quot MAR quot                       month   models CharField          max length 2          choices Month choices          default Month JAN        Usage    gt  gt  gt  obj   MyModel objects create month  1    gt  gt  gt  assert obj month    obj Month JAN  gt  gt  gt  assert MyModel Month obj month  label     JANUARY   gt  gt  gt  assert MyModel objects filter month MyModel Month JAN  count    gt   1   gt  gt  gt  obj2   MyModel month MyModel Month FEB   gt  gt  gt  assert obj2 get month display      obj2 Month obj2 month  label

[python] How to properly use the "choices" field option in Django

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