I want to store datetime in peewee.DateTimeField(), I use datetime.datetime.now() in that field as default but it can't work

Question

this code cannot work and give json serializable error

  class Bank(peewee.Model): // create Bank table
        bank_id     = peewee.PrimaryKeyField()
        bank_name   = peewee.CharField()
        account_no  = peewee.CharField()
        ifc_code    = peewee.CharField()
        swift_code  = peewee.CharField(null = True)
        modify_date = peewee.DateTimeField(default=datetime.datetime.now(),formats=['%Y-%m-%d'])/*date in yyyy-mm-dd formate*/
        status      = peewee.IntegerField(default = 0)

        class Meta:
            database = db

Answer 1

This answer is very incorrect - please see my answer below (@coleifer).

---

The default date that you are providing is not a datetime object. Rather it's a string!

modify_date = peewee.DateTimeField(default=datetime.datetime.now().strftime('%Y-%m-%d'))

type(datetime.datetime.now().strftime('%Y-%m-%d')) --> str

You can pass default current datetime object like this:

date = datetime.datetime.now().strftime('%Y-%m-%d')
need_date = datetime.strptime(date, '%Y-%m-%d')

modify_date = peewee.DateTimeField(default=need_date)

or

peewee.DateTimeField(default=datetime.datetime.now)

Answer 2

It looks like non-timezone aware datetimes work fine, so if you're using UTC then you can store datetime.utcnow() as that returns the current UTC date and time with tzinfo None i.e. as a "naive" datetime object.

I found this solution to store and retrieve the timezone aware field as text, however it's not ideal as the datetime object isn't being stored.

from datetime import datetime
from peewee import *


class TimestampTzField(Field):
    """
    A timestamp field that supports a timezone by serializing the value
    with isoformat.
    """

    field_type = "TEXT"

    def db_value(self, value: datetime) -> str:
        if value:
            return value.isoformat()

    def python_value(self, value: str) -> str:
        if value:
            return datetime.fromisoformat(value)

https://compileandrun.com/python-peewee-timezone-aware-datetime/

Answer 3

If you want to store a date, use the DateField. Also, the default needs to be a callable -- in other words, leave OFF the parentheses!

class Bank(peewee.Model): // create Bank table
    bank_id     = peewee.PrimaryKeyField()
    bank_name   = peewee.CharField()
    account_no  = peewee.CharField()
    ifc_code    = peewee.CharField()
    swift_code  = peewee.CharField(null = True)
    modify_date = peewee.DateField(default=datetime.date.today)
    status      = peewee.IntegerField(default = 0)

    class Meta:
        database = db

When it comes time to serialize this as Json, just use a custom json formatter that can handle python datetime.date objects. This is the proper way. You should always store your data using the appropriate format and worry about presentation (and serialization) in another layer.

It is very simple to extend Python's json serializer to handle unsupported types:

def convert_date(o):
    if isinstance(o, datetime.date):
        return o.__str__()

json.dumps(my_obj, default=convert_date)