The important method is .validate(), of course. It gets passed a dictionary of the (processed) values from the form. If you have .validate_partial_form set to True, then it will get the incomplete values as well -- use .has_key() to test if the field was able to process any particular field.

Anyway, .validate() should return a string or a dictionary. If a string, it's an error message that applies to the whole form. If not, then it should be a dictionary of fieldName: errorMessage. The special key "form" is the error message for the form as a whole (i.e., a string is equivalent to {"form": string}).

Return None on no errors.

Messages

badType:

The input must be a string (not a %(type)s: %(value)r)

empty:

Please enter a value

noneType:

The input must be a string (not None)