WTForms field defaults suddenly don't work

Question

I have the following code:

class ReconForm(Form):
    compressedFilePath = StringField('Compressed File Path', [validators.Required()] )

and I instantiate it like this:

form = ReconForm()
form.compressedFilePath.default = 'hey'

It does nothing. It used to set the default value to hey but then it stopped and I have no idea why.

If I print form.compressedFilePath.default then it prints the correct value. If I set a default in the field constructor the template renders the correct value. Otherwise it just does nothing and it's driving me crazy.

What am I doing wrong?

Answer 1

Here are the two ways I know to set a default value for a field using WTForms.

1. To set the value to be the default for all instances of a form, declare the value in the field's definition.

   class ReconForm(Form):
       compressedFilePath = StringField(
           'Compressed File Path', [validators.Required()], default='hi')
   
   form = ReconForm()
   

   To verify:

   assert 'value="hi"' in str(form.compressedFilePath)
   

2. To set the value to be the default for just a specific instance of the form, specify the value at instantiation.

   class ReconForm(Form):
       compressedFilePath = StringField(
           'Compressed File Path', [validators.Required()])
   
   form = ReconForm(compressedFilePath='hi')
   

   To verify:

   assert 'value="hi"' in str(form.compressedFilePath)
   

Answer 2

Really old question but there is an easier way - just call process() on your form after setting the default value.