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djangomanytomanyfield

variable length many to many

I want to know how to count the number of "keys" a "keyboard"

class Key(models.Model):
    name = models.CharField(max_length = 20)

class Keyboard(models.Model):
    name = models.CharField(max_length = 20)
    keys = models.ManyToManyField(Key)

I found a similar question but do not know if it can be modified for what I need, which is how many eleementos form a ManyToMany

count values from manytomanyfield

Solution

  • To get the count of keys objects associated with a Keyboard instance, you can use .count()

    keyboard_object.keys.all() gives the associated Key instances for a keyboard_object.

    We now apply .count() on it to get the number of Key objects associated with it.

    keyboard_object.keys.all().count() # gives the count

    (Even keyboard_object.keys.count() will work unless the default Key queryset is changed.)