'initial' argument must come first when creating django form??

Question

I have this working code

f = SomeForm(request.POST)

When I tried to modify it into

f = SomeForm(request.POST, initial={'spam', 4})

it didnt work, the 'initial' wasnt selected ('spam' is a ModelChoiceField), but when I tried

f = SomeForm(initial={'spam', 4})

it worked (selected value was correct). Am I missing something here? If it matters, heres what its init method looks like

def __init__(self, *a, **ka):
    super(SomeForm, self).__init__(*a, **ka)
    ....#more codes

Is there a way to make the initial data works without having to remove the first argument? Thank you

EDIT : it doesnt have to be "initial", as long as I can put some pre-determined value on ModelChoiceField. The condition = There is a request.POST, but the form hasnt been submitted (the post came from another page)

Answer 1

You don't need to pass initial if the form has been posted. Check request.method and instantiate the form accordingly.

Answer 2

It turned out I only had to change the data attribute. Use copy method to make QueryDict mutable

post = request.POST.copy()

f = SomeForm(post)
f.data['spam'] = 4