How to convert and auto-generate data in same models when calling .create()?

Question

Notice that test.py use .create() to setup DB before test.

    song = Song.objects.create(
        title="Don't Stop Believing",
        artist="Journey",
        length=250,
        performer=self.performer)

At the time of .create() was called. The Songs model need to convert "length" value (250) to timedelta object and store in in DurationField. My code end up with

TypeError: int() argument must be a string or a number, not 'IntegerField'

So, How to auto-generate "duration" by converting value pass in kwargs "length"? at the time instance was created?

If the "length" attribute has to be updated in future, How to make "duration" auto-update itself?

PS: I spend sometimes to understand override init , Its just too complicated. If that is what need to be done, Please give me lot of resources and example.

songs/models.py

from django.db import models
from datetime import timedelta

# Write your models here


class Song(models.Model):
    title = models.CharField(max_length=255)
    artist = models.CharField(max_length=255)
    performer = models.ForeignKey('Performer')
    length = models.IntegerField()
    duration = models.DurationField(auto_created=True, default=timedelta(minutes=int(length)))

    def __str__(self):
        return str(self.title) + ' by ' + str(self.artist)

class Performer(models.Model):
    name = models.CharField(max_length=255)

    def __str__(self):
        return str(self.name)

songs/views.py

from django.shortcuts import render
from .models import Song, Performer


def song_list(request):
    songs = Song.objects.all()
    return render(request, 'songs/song_list.html', {'songs':songs})

def song_detail(request, pk):
    song = Song.objects.get(pk=pk)
    return render(request, 'songs/song_detail.html', {'song':song})

def performer_detail(request, pk):
    performer = Performer.objects.get(pk=pk)
    return render(request, 'songs/performer_detail.html', {'performer':perfor

songs/templates/songs/performer_detail.html

{% extends 'base.html' %}

{% block title %}{{ performer }}{% endblock %}

{% block content %}
<h2>{{ performer }}</h2>
{% endblock %}

Answer 1 · 2016-10-31T16:31:25Z

October 31, 2016 4:31pm

Why do you need a separate duration field if you already have a length field, which holds a number of seconds the song is long?

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Harin Yuwarattanaporn

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How to convert and auto-generate data in same models when calling .create()?

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Tatiana Vasilevskaya

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Harin Yuwarattanaporn

Harin Yuwarattanaporn