form validation (function and class examples)

validate_form.py

def validate_name_as_caps(name):
    """
    raise ValueError and pass respective message
    """
    if name.upper() != name:
        raise ValueError("Name is not capitalized")
    return name


validators = {
    'name': validate_name_as_caps
}


def validate_form(form, validators):
    output = {
        'valid': {},
        'errors': {},
        'skipped': []  # stores fields that have no corresponding validator function
    }

    for field, val in form.items():
        try:
            if field in validators:
                output['valid'][field] = validators[field](val)
            else:
                output['valid'][field] = val
                output['skipped'].append(field)
        except ValueError as error:
            output['errors'][field] = str(error)

    return output


good_form = {
    'name': 'UPPERCASE',
    'skipped': 'no validator'
}

bad_form = {
    'name': 'lowercase',
    'skipped': 'no validator'
}

good_output = validate_form(good_form, validators)
bad_output = validate_form(bad_form, validators)

print('good output:', good_output)
print('bad output:', bad_output, '\n')

"""
or as a class
"""


class FormValidator:
    """
    pass a validators dictionary with validation functions 
    """
    def __init__(self, validators):
        self.validators = validators
        self.valid = {}
        self.errors = {}
        self.skipped = []  # for fields that have no validator

    def validate(self, form):
        for field, val in form.items():
            try:
                if field in self.validators:
                    self.valid[field] = self.validators[field](val)
                else:
                    self.valid[field] = val
                    self.skipped.append(field)
            except ValueError as error:
                self.errors[field] = str(error)


good_validator = FormValidator(validators)
good_validator.validate(good_form)
print(f'good values: {good_validator.valid}\n\
good errors: {good_validator.errors}\n\
skipped fields: {good_validator.skipped}\n')

bad_validator = FormValidator(validators)
bad_validator.validate(bad_form)
print(f'bad values: {bad_validator.valid}\n\
bad errors: {bad_validator.errors}\n\
skipped fields: {good_validator.skipped}')