What is the difference between initial and instance in django formset?

Question

What is the difference between initial and instance in django formset?

When to use which?

What should I use to show the prepopulated data in an invalid form in the following case:

formset= FormSet(initial=[{'a':list.b} for list in listslist])
if request.method =='post':
    formset = FormSet(request.post, ---instance/initial? ---)

Answer 1

initial is to set defaults for new forms.

instances is to set models instances you use as initial models, which will be populated with entered data. You can use this attribute to edit your model instances.