python - How do you set a default value for a WTForms SelectField?

Question

When attempting to set the default value of a SelectField with WTForms, I pass in value to the 'default' parameter like so.

class TestForm(Form):
  test_field = SelectField("Test: ", choices=[(1, "Abc"), (2, "Def")], default=2)

I have also tried the following.

class TestForm(Form):
  test_field = SelectField("Test: ", choices=[(1, "Abc"), (2, "Def")], default=(2, "Def"))

Neither set the default selected field to "Def." This works for other kinds of Fields such as TextField. How do you set the default value for a SelectField?'

Answer 1

I believe this problem is caused by the Field's data attribute overriding the default with something that WTForms doesn't understand (e.g. a DB model object -- it expects an int). This would happen if you have populated your form in the constructor like so:

form = PostForm(obj=post)

the solution is to manually set the data attribute after the form has been populated:

form = PostForm(obj=post)
form.category.data = (post.category.id
                      if page.category
                      else 0) # I make 0 my default