现在直接回答:检查字段的值是否已经改变的一种方法是在保存实例之前从数据库获取原始数据。想想这个例子:

class MyModel(models.Model):
    f1 = models.CharField(max_length=1)

    def save(self, *args, **kw):
        if self.pk is not None:
            orig = MyModel.objects.get(pk=self.pk)
            if orig.f1 != self.f1:
                print 'f1 changed'
        super(MyModel, self).save(*args, **kw)

同样的事情也适用于处理表单。您可以在ModelForm的clean或save方法中检测到它:

class MyModelForm(forms.ModelForm):

    def clean(self):
        cleaned_data = super(ProjectForm, self).clean()
        #if self.has_changed():  # new instance or existing updated (form has data to save)
        if self.instance.pk is not None:  # new instance only
            if self.instance.f1 != cleaned_data['f1']:
                print 'f1 changed'
        return cleaned_data

    class Meta:
        model = MyModel
        exclude = []

现在直接回答:检查字段的值是否已经改变的一种方法是在保存实例之前从数据库获取原始数据。想想这个例子:

class MyModel(models.Model):
    f1 = models.CharField(max_length=1)

    def save(self, *args, **kw):
        if self.pk is not None:
            orig = MyModel.objects.get(pk=self.pk)
            if orig.f1 != self.f1:
                print 'f1 changed'
        super(MyModel, self).save(*args, **kw)

同样的事情也适用于处理表单。您可以在ModelForm的clean或save方法中检测到它:

class MyModelForm(forms.ModelForm):

    def clean(self):
        cleaned_data = super(ProjectForm, self).clean()
        #if self.has_changed():  # new instance or existing updated (form has data to save)
        if self.instance.pk is not None:  # new instance only
            if self.instance.f1 != cleaned_data['f1']:
                print 'f1 changed'
        return cleaned_data

    class Meta:
        model = MyModel
        exclude = []

本质上，你想要重写模型的__init__方法。模型，以便保留原始值的副本。这使得您不必再执行另一个DB查找(这总是一件好事)。

    class Person(models.Model):
        name = models.CharField()

        __original_name = None

        def __init__(self, *args, **kwargs):
            super().__init__(*args, **kwargs)
            self.__original_name = self.name

        def save(self, force_insert=False, force_update=False, *args, **kwargs):
            if self.name != self.__original_name:
                # name changed - do something here

            super().save(force_insert, force_update, *args, **kwargs)
            self.__original_name = self.name

有一个属性__dict__，它将所有字段作为键，并将值作为字段值。所以我们可以比较其中两个

只需将模型的save函数更改为下面的函数即可

def save(self, force_insert=False, force_update=False, using=None, update_fields=None):
    if self.pk is not None:
        initial = A.objects.get(pk=self.pk)
        initial_json, final_json = initial.__dict__.copy(), self.__dict__.copy()
        initial_json.pop('_state'), final_json.pop('_state')
        only_changed_fields = {k: {'final_value': final_json[k], 'initial_value': initial_json[k]} for k in initial_json if final_json[k] != initial_json[k]}
        print(only_changed_fields)
    super(A, self).save(force_insert=False, force_update=False, using=None, update_fields=None)

使用示例:

class A(models.Model):
    name = models.CharField(max_length=200, null=True, blank=True)
    senior = models.CharField(choices=choices, max_length=3)
    timestamp = models.DateTimeField(null=True, blank=True)

    def save(self, force_insert=False, force_update=False, using=None, update_fields=None):
        if self.pk is not None:
            initial = A.objects.get(pk=self.pk)
            initial_json, final_json = initial.__dict__.copy(), self.__dict__.copy()
            initial_json.pop('_state'), final_json.pop('_state')
            only_changed_fields = {k: {'final_value': final_json[k], 'initial_value': initial_json[k]} for k in initial_json if final_json[k] != initial_json[k]}
            print(only_changed_fields)
        super(A, self).save(force_insert=False, force_update=False, using=None, update_fields=None)

产生只包含已更改字段的输出

{'name': {'initial_value': '1234515', 'final_value': 'nim'}, 'senior': {'initial_value': 'no', 'final_value': 'yes'}}

如果你正在使用一个表单，你可以使用表单的changed_data (docs):

class AliasForm(ModelForm):

    def save(self, commit=True):
        if 'remote_image' in self.changed_data:
            # do things
            remote_image = self.cleaned_data['remote_image']
            do_things(remote_image)
        super(AliasForm, self).save(commit)

    class Meta:
        model = Alias

这在Django 1.8中是适用的

def clean(self):
    if self.cleaned_data['name'] != self.initial['name']:
        # Do something