Update value of a certail column in django post_save signals

Question

I have a class Video whose structure is as below:

class Video(models.Model):
    video = models.FileField(upload_to="media_items/video", blank=True)
    video_mp4 = models.CharField(blank=True, max_length=500)

    def __unicode__(self):
        return unicode(self.video.name) or u''

and signals.py is as

@receiver(post_save, sender = Video)
def insert_video_mp4(sender, instance, created, **kwargs):
    if os.path.exists(created_path):
        #some code
    else:
        #some code to insert value in video_mp4 column

I want to update the value of video_mp4 as explained above in post_save signals. Please let me know how to achieve this. I am getting the below error

RuntimeError at /admin/blog/video/8/change/
maximum recursion depth exceeded while calling a Python object
Request Method: POST
Request URL:    http://localhost:8000/admin/blog/video/8/change/
Django Version: 1.10.5
Exception Type: RuntimeError
Exception Value:    
maximum recursion depth exceeded while calling a Python object
Exception Location: /Users/anaconda2/lib/python2.7/site-packages/django/db/models/fields/__init__.py in __eq__, line 462
Python Executable:  /Users/anaconda2/bin/python
Python Version: 2.7.15
Python Path:    
['/Users/TechnopleSolutions/Desktop/matrix-server-master',
 '/Users/anaconda2/lib/python27.zip',
 '/Users/anaconda2/lib/python2.7',
 '/Users/anaconda2/lib/python2.7/plat-darwin',
 '/Users/anaconda2/lib/python2.7/plat-mac',
 '/Users/anaconda2/lib/python2.7/plat-mac/lib-scriptpackages',
 '/Users/anaconda2/lib/python2.7/lib-tk',
 '/Users/anaconda2/lib/python2.7/lib-old',
 '/Users/anaconda2/lib/python2.7/lib-dynload',
 '/Users/anaconda2/lib/python2.7/site-packages',
 '/Users/anaconda2/lib/python2.7/site-packages/aeosa']

Why do you need signals here? What's your logic ? Can you explain it? — JPG, Aug 08 '18 at 09:54
I am doing some operation after that I'm updating the column — daemon, Aug 08 '18 at 09:56
Its a funny problem. The 'Stack is Overflowing' because of recursive save call and post_save call. — Sayok88, Aug 08 '18 at 10:15

JPG · Answer 1 · 2018-08-08T10:02:22.253

2

instance is corresponding Video object here.


@receiver(post_save, sender = Video)
def insert_video_mp4(sender, instance, created, **kwargs):
    if os.path.exists(created_path):
        #some code
    else:
        instance.video_mp4="some value"
        instance.save()

UPDATE
The above solution will cause a maximum recursion depth exceeded while calling a Python object error. So, do your logic save() method of model by overriding it as,

class Video(models.Model):
    video = models.FileField(upload_to="media_items/video", blank=True)
    video_mp4 = models.CharField(blank=True, max_length=500)

    def save(self, *args, **kwargs):
        if os.path.exists(created_path):
        # some code
        else:
            self.video_mp4 = "some text"
        super().save(*args, **kwargs)

    def __unicode__(self):
        return unicode(self.video.name) or u''

Note: It's not a good idea to call .save() method inside a post_save signal

edited Aug 08 '18 at 10:02

answered Aug 08 '18 at 09:39

JPG

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I have tried this but getting error as "Exception Value: maximum recursion depth exceeded while calling a Python object" – daemon Aug 08 '18 at 09:40
can you add full traceback to your question ? – JPG Aug 08 '18 at 09:41
@daemon Did you override anything? – JPG Aug 08 '18 at 09:48
No, not overriding anything – daemon Aug 08 '18 at 09:51
Ok. Why do you need signals here? What's your logic ? Can you explain it? – JPG Aug 08 '18 at 09:53

score 0 · Answer 2 · answered Aug 08 '18 at 12:13

0

Thanks @Jerin Peter George But found a very good solution for that

Check this

answered Aug 08 '18 at 12:13

daemon

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Update value of a certail column in django post_save signals

2 Answers2