WTForms custom field for dollar values

Question

I'm new to WTForms. I wanted to create a new type of field called DollarField which would allow "$" and commas. I would then strip these out and save the value.

I did this which strips off the "$" and removes commas but now all the normal validation that works for DecimalField (e.g. catching cases if the user types in "asda") don't work.

class DollarField(DecimalField):
    def process_formdata(self, valuelist):
        if len(valuelist) == 1:
            self.data = [valuelist[0].strip('$').replace(',', '')]
        else:
            self.data = []

Answer 1

Your issue is that because you override process_formdata, you are replacing the default processing code (which attempts to convert the string into a decimal, and thus raises an error if it cannot) with your own code. You'll want to make sure that your implementation of process_formdata manually calls the parent's process_formdata method so that its logic is also run, like so...

class DollarField(DecimalField):
    def process_formdata(self, valuelist):
        if len(valuelist) == 1:
            self.data = [valuelist[0].strip('$').replace(',', '')]
        else:
            self.data = []

        # Calls "process_formdata" on the parent types of "DollarField",
        # which includes "DecimalField"
        super(DollarField).process_formdata(self.data)