Estudando classes e properties.

setter_exemplo.py

# -*- coding: utf-8 -*-


class MyClass(object):

    error_msgs = {
        'integer': "This doesn't look like an integer."
    }

    def __init__(self, default=0, raise_errors=True):
        self.default = default
        self.raise_errors = raise_errors
        self.errors = []
        self._value = None

    def clean_errors(self):
        self.errors = []

    @property
    def value(self):
        return self._value or self.default

    @value.setter
    def value(self, value):
        try:
            int(value)
        except (TypeError, ValueError):
            if self.raise_errors:
                raise Exception(self.error_msgs.get('integer'))
            else:
                self.errors.append(self.error_msgs.get('integer'))
                return
        self._value = int(value)


if __name__ == '__main__':
    klass = MyClass(raise_errors=False)
    print klass.value
    klass.value = 10
    print klass.value
    klass.value = '200'
    print klass.value
    klass.value = '200-'
    klass.value = '200-'
    klass.value = '200-'
    print klass.errors
    klass.clean_errors()
    klass.value = '200-'
    print klass.value
    print klass.errors