Django datetime issues default datetime now

Question

I have the below db model   from datetime import datetime      class TermPayment models Model         I have excluded fields that are irrelevant to the question     date   models DateTimeField default datetime now    blank True    I add a new instance by using the below   tp   TermPayment objects create   kwargs    My issue  all records in database have the same value in date field  which is the date of the first payment  After the server restarts  one record has the new date and the other records have the same as the first  It looks as if some data is cached  but I can t find where   database  mysql 5 1 25  django v1 1 1

User · Answer

Instead of using datetime now you should be really using from django utils timezone import now  Reference    Documentation for django utils timezone now   so go for something like this   from django utils timezone import now   created date   models DateTimeField default now  editable False

User · Answer

datetime now   is being evaluated once  when your class is instantiated  Try removing the parenthesis so that the function datetime now is returned and THEN evaluated  I had the same issue with setting default values for my DateTimeFields and wrote up my solution here

User · Answer

David had the right answer  The parenthesis    makes it so that the callable timezone now   is called every time the model is evaluated  If you remove the    from timezone now    or datetime now    if using the naive datetime object  to make it just this   default timezone now   Then it will work as you expect      New objects will receive the current date when they are created  but the date won t be overridden every time you do manage py makemigrations migrate   I just encountered this  Much thanks to David

User · Answer

The answer to this one is actually wrong   Auto filling in the value  auto now auto now add isn t the same as default    The default value will actually be what the user sees if its a brand new object   What I typically do is       date   models DateTimeField default datetime now  editable False     Make sure  if your trying to represent this in an Admin page  that you list it as  read only  and reference the field name  read only    date    Again  I do this since my default value isn t typically editable  and Admin pages ignore non-editables unless specified otherwise   There is certainly a difference however between setting a default value and implementing the auto add which is key here   Test it out

User · Answer

From the documentation on the django model default field   The default value for the field  This can be a value or a callable object  If callable it will be called every time a new object is created   Therefore following should work   date   models DateTimeField default datetime now blank True

User · Answer

In Django 3 0  auto now add seems to work with auto now  reg date models DateField auto now True blank True

User · Answer

The datetime now   is evaluated when the class is created  not when new record is being added to the database   To achieve what you want define this field as   date   models DateTimeField auto now add True    This way the date field will be set to current date for each new record

User · Answer

it looks like datetime now   is being evaluated when the model is defined  and not each time you add a record   Django has a feature to accomplish what you are trying to do already   date   models DateTimeField auto now add True  blank True    or  date   models DateTimeField default datetime now  blank True    The difference between the second example and what you currently have is the lack of parentheses  By passing datetime now without the parentheses  you are passing the actual function  which will be called each time a record is added  If you pass it datetime now    then you are just evaluating the function and passing it the return value   More information is available at Django s model field reference

User · Answer

From the Python language reference  under Function definitions      Default parameter values are evaluated when the function definition is executed  This means that the expression is evaluated once  when the function is defined  and that that same    pre-computed    value is used for each call    Fortunately  Django has a way to do what you want  if you use the auto now argument for the DateTimeField   date   models DateTimeField auto now True    See the Django docs for DateTimeField

[python] Django datetime issues (default=datetime.now())

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