Django删除FileField [英] Django delete FileField

问题描述

我正在Django建立一个网络应用程序。我有一个上传文件的模型，但我不能删除它。这是我的代码：

  class Song（models.Model）：
 name = models.CharField（blank = True ，max_length = 100）
 author = models.ForeignKey（User，to_field ='id'，related_name =id_user2）
 song = models.FileField（upload_to ='/ songs /'）
 image = models.ImageField（upload_to ='/ pictures /'，blank = True）
 date_upload = models.DateField（auto_now_add = True）
 
 def delete（self，* args，*删除模型
存储，path = self.song.storage，self.song.path 
＃删除模型前的文件
 super（Song，self）.delete（* args，** kwargs）
＃删除模型后的文件
 storage.delete（path）
  

然后，在python manage.py shell中我这样做：

  song = Song.objects.get（pk = 1）
 song.delete（）
  

它从数据库中删除但不从数据库中删除服务器上的文件。
我还可以尝试什么？

谢谢！

解决方案

p>在Django 1.3之前，当您删除相应的模型实例时，文件将自动从文件系统中删除。您可能正在使用较新的Django版本，因此您必须自行实现从文件系统中删除该文件。

您可以通过以下几种方法之一：它正在使用 pre_delete 或 post_delete 信号。

示例

我现在选择的方法是混合使用 post_delete 和 pre_save 信号，这样就可以删除每当相应的模型被删除或更改文件时过时的文件。

根据假设的 MediaFile 模型：

 导入os 
 import uuid 
 
 from django.db import models 
 from django.dispatch import receiver 
 from django.utils.translation import ugettext_lazy as _ 
 
 
 class MediaFile（models.Model）：
 file = models.FileField（_（file），
 upload_to = lambda实例，filename：str（uuid.uuid4 ））
 
 
＃这两个文件系统在不需要时自动删除文件：
 
 @receiver（models.signals.post_delete，sender = MediaFile） 
 def auto_delete_file_on_delete（sender，instance，** kwargs）：

从文件系统
中删除文件，当对应的M ediaFile`对象被删除。 

 if instance.file：
如果os.path.isfile（instance.file.path）：
 os.remove（instance.file.path）
 
 @receiver（models.signals.pre_save，sender = MediaFile）
 def auto_delete_file_on_change（sender，instance，** kwargs）：

删除旧文件文件系统
当对应的MediaFile对象被更新
与新文件。 

 if not instance.pk：
 return False 
 
 try：
 old_file = MediaFile.objects.get（pk = instance.pk ）.file 
除了MediaFile.DoesNotExist：
 return False 
 
 new_file = instance.file 
如果不是old_file == new_file：
如果os.path .isfile（old_file.path）：
 os.remove（old_file.path）
  

• 边缘案例：如果您的应用上传新文件，并将模型实例指向新文件，而不调用 save（）（例如批量更新 QuerySet ），因为信号不会被运行，旧的文件将会继续存在，如果使用传统的文件处理方法，则不会发生。



• 编码风格：本示例使用文件作为字段名称，这不是一个好的风格，因为它与内置的文件对象标识符

另请参见

• FileField.delete（） （Django 1.11 model field reference）

  
  

  请注意，当模型被删除时，相关文件不会被删除。如果您需要清理孤立的文件，那么您需要自己处理（例如，使用自定义管理命令，可以手动运行或通过例如cron定期运行）。

  
  




• 为什么Django不会自动删除文件：在Django 1.3的发行说明中的​​条目

  
  

  在早期的Django版本中，当包含 FileField 的模型实例被删除时， FileField 本身也可以从后端存储中删除文件。这为几个数据丢失场景打开了大门，包括回滚事务和引用同一文件的不同模型上的字段。在Django 1.3中，当一个模型被删除时，不会调用 FileField 的 delete（）方法。如果您需要清理孤立的文件，您需要自己处理（例如，使用可以手动运行或定期运行的定制管理命令，例如通过cron定期运行）。

  
  




• 仅使用 pre_delete 信号的示例

I'm building a web app in Django. I have a model that uploads a file, but I can not delete it. Here is my code:

class Song(models.Model):
    name = models.CharField(blank=True, max_length=100)
    author = models.ForeignKey(User, to_field='id', related_name="id_user2")
    song = models.FileField(upload_to='/songs/')
    image = models.ImageField(upload_to='/pictures/', blank=True)
    date_upload = models.DateField(auto_now_add=True)

    def delete(self, *args, **kwargs):
        # You have to prepare what you need before delete the model
        storage, path = self.song.storage, self.song.path
        # Delete the model before the file
        super(Song, self).delete(*args, **kwargs)
        # Delete the file after the model
        storage.delete(path)

Then, in "python manage.py shell" I do this:

song = Song.objects.get(pk=1)
song.delete()

It deletes from database but not the file on server. What else can I try?

Thanks!

解决方案

Before Django 1.3, the file was deleted from the filesystem automatically when you deleted the corresponding model instance. You are probably using a newer Django version, so you'll have to implement deleting the file from the filesystem yourself.

You can do that in a few ways, one of which is using a pre_delete or post_delete signal.

Example

My method of choice currently is a mix of post_delete and pre_save signals, which makes it so that obsolete files are deleted whenever corresponding models are deleted or have their files changed.

Based on a hypothetical MediaFile model:

import os
import uuid

from django.db import models
from django.dispatch import receiver
from django.utils.translation import ugettext_lazy as _


class MediaFile(models.Model):
    file = models.FileField(_("file"),
        upload_to=lambda instance, filename: str(uuid.uuid4()))


# These two auto-delete files from filesystem when they are unneeded:

@receiver(models.signals.post_delete, sender=MediaFile)
def auto_delete_file_on_delete(sender, instance, **kwargs):
    """
    Deletes file from filesystem
    when corresponding `MediaFile` object is deleted.
    """
    if instance.file:
        if os.path.isfile(instance.file.path):
            os.remove(instance.file.path)

@receiver(models.signals.pre_save, sender=MediaFile)
def auto_delete_file_on_change(sender, instance, **kwargs):
    """
    Deletes old file from filesystem
    when corresponding `MediaFile` object is updated
    with new file.
    """
    if not instance.pk:
        return False

    try:
        old_file = MediaFile.objects.get(pk=instance.pk).file
    except MediaFile.DoesNotExist:
        return False

    new_file = instance.file
    if not old_file == new_file:
        if os.path.isfile(old_file.path):
            os.remove(old_file.path)

• Edge case: if your app uploads a new file and points model instance to the new file without calling save() (e.g. by bulk updating a QuerySet), the old file will keep lying around because signals won’t be run. This doesn’t happen if you use conventional file handling methods.
• I think one of the apps I’ve built has this code in production but nevertheless use at your own risk.
• Coding style: this example uses file as field name, which is not a good style because it clashes with the built-in file object identifier.

See also

• FileField.delete() (Django 1.11 model field reference)

  Note that when a model is deleted, related files are not deleted. If you need to cleanup orphaned files, you’ll need to handle it yourself (for instance, with a custom management command that can be run manually or scheduled to run periodically via e.g. cron).

• Why Django doesn’t delete files automatically: entry in release notes for Django 1.3

  In earlier Django versions, when a model instance containing a FileField was deleted, FileField took it upon itself to also delete the file from the backend storage. This opened the door to several data-loss scenarios, including rolled-back transactions and fields on different models referencing the same file. In Django 1.3, when a model is deleted the FileField’s delete() method won’t be called. If you need cleanup of orphaned files, you’ll need to handle it yourself (for instance, with a custom management command that can be run manually or scheduled to run periodically via e.g. cron).

• Example of using a pre_delete signal only

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