How do I know in Django’s html if the view is filled with instance?

Question

I am starting my studies in Django, in a CRUD, I created a single form that I would like to use for both creation and change.

I would like to change the text of the button depending on the function to be assigned to the form. In Laravel I checked if the object passed was empty to know if it is creation or change.

In Django I did so, in views.py I went through the render the value of Submit

return render(request, 'form.html', {'form':form, 'btn_submit': 'Cadastrar'})

and

return render(request, 'form.html', {'form':form, 'btn_submit': 'Alterar'})

In html I simply used the value with an interpolation

<!-- form.html -->
<input type="submit" value="{{ btn_submit }}">

I would appreciate the help, if you could point out to me best methods or best practices, it would be very helpful in my learning. Thank you.