Django Override save for model

Question

Before saving model I m re-size a picture  But how can I check if new picture added or just description updated  so I can skip rescaling every time the model is saved   class Model model Model       image models ImageField upload to  folder       thumb models ImageField upload to  folder       description models CharField         def save self   args    kwargs           if self image              small rescale image self image width 100 height 100              self image small SimpleUploadedFile name small pic          super Model  self  save  args    kwargs    I want to rescale only if new image loaded or image updated  but not when description updated

User · Answer

Check the model s pk field   If it is None  then it is a new object   class Model model Model       image models ImageField upload to  folder       thumb models ImageField upload to  folder       description models CharField         def save self   args    kwargs           if  form  in kwargs              form kwargs  form           else              form None          if self pk is None and form is not None and  image  in form changed data              small rescale image self image width 100 height 100              self image small SimpleUploadedFile name small pic          super Model  self  save  args    kwargs    Edit  I ve added a check for  image  in form changed data   This assumes that you re using the admin site to update your images   You ll also have to override the default save model method as indicated below   class ModelAdmin admin ModelAdmin       def save model self  request  obj  form  change           obj save form form

User · Answer

Some thoughts   class Model model Model        image models ImageField upload to  folder       thumb models ImageField upload to  folder       description models CharField        def set image self  val           self  image   val         self  image changed   True            Or put whole logic in here         small   rescale image self image width 100 height 100          self image small SimpleUploadedFile name small pic       def get image self           return self  image      image   property get image  set image         this is not needed if small image is created at set image     def save self   args    kwargs           if getattr self    image changed   True               small rescale image self image width 100 height 100              self image small SimpleUploadedFile name small pic          super Model  self  save  args    kwargs    Not sure if it would play nice with all pseudo-auto django tools  Example  ModelForm  contrib admin etc

User · Answer

What I did to achieve the goal was to make this      I added an extra command argument that defaults to blank def save self  extra command      args    kwargs     and below the save   method is this      override the save method to create an image thumbnail if self image and extra command     skip creating photo thumbnail         your logic here   so when i edit some fields but not editing the image  I put this    Model save  skip creating photo thumbnail     you can replace the  skip creating photo thumbnail  with  im just editing the description  or a more formal text   Hope this one helps

User · Answer

Query the database for an existing record with the same PK  Compare the file sizes and checksums of the new and existing images to see if they re the same

User · Answer

You may supply extra argument for confirming a new image is posted  Something like   def save self  new image False   args    kwargs       if new image          small rescale image self image width 100 height 100          self image small SimpleUploadedFile name small pic      super Model  self  save  args    kwargs    or pass request variable  def save self  request False   args    kwargs       if request and request FILES get  image  False           small rescale image self image width 100 height 100          self image small SimpleUploadedFile name small pic      super Model  self  save  args    kwargs    I think these wont break your save when called simply   You may put this in your admin py so that this work with admin site too  for second of above solutions    class ModelAdmin admin ModelAdmin                 def save model self  request  obj  form  change            instance   form save commit False          instance save request request          return instance

User · Answer

In new version it is like this     def validate self  attrs       has unknown fields   set self initial data  - set self fields keys        if has unknown fields          raise serializers ValidationError  Do not send extra fields       return attrs

User · Answer

I have found one another simple way to store the data into the database  models py  class LinkModel models Model       link   models CharField max length 500      shortLink   models CharField max length 30 unique True    In database I have only 2 variables  views py  class HomeView TemplateView       def post self request   args    kwargs           form   LinkForm request POST           if form is valid                text   form cleaned data  link     text for link          dbobj   LinkModel           dbobj link   text         self no   self gen generateShortLink     no for shortLink         dbobj shortLink   str self no          dbobj save             Saving from views py   In this I have created the instance of model in views py only and putting saving data into 2 variables from views only

[python] Django. Override save for model

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