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[EDIT] FILE: datatype.py

from .exception import DataTypeError

__all__ = ("DataType", "String", "Integer", "Float", "Boolean", "List", "Choice")

class DataType(object):
    def sanitize(self, value):
        raise NotImplementedError()

def is_valid(self, value):
        try:
            self.sanitize(value)
        except DataTypeError:
            return False
        else:
            return True

class String(DataType):
    def sanitize(self, value):
        return None if value is None else str(value)

class Integer(DataType):
    def sanitize(self, value):
        if value is not None:
            try:
                value = int(value)
            except:
                raise DataTypeError('"%s" is not valid Integer' % value)
        return value

class Float(DataType):
    def sanitize(self, value):
        if value is not None:
            try:
                value = float(value)
            except:
                raise DataTypeError('"%s" is not valid Float' % value)
        return value

class Boolean(DataType):
    TRUTHY_STRINGS = ("Y", "YES", "T", "TRUE", "ON", "1")
    FALSY_STRINGS = ("", "N", "NO", "F", "FALSE", "OFF", "0")

def sanitize(self, value):
        if value is None or isinstance(value, bool):
            return value

if isinstance(value, int):
            return True if value else False

if isinstance(value, str) and value:
            value = value.strip().upper()
            if value in self.TRUTHY_STRINGS:
                return True
            elif value in self.FALSY_STRINGS:
                return False
            else:
                raise DataTypeError('Could not coerce "%s" to a Boolean' % (value,))

return True if value else False

class List(DataType):
    def __init__(self, subtype):
        super(List, self).__init__()
        if isinstance(subtype, DataType):
            self.subtype = subtype
        elif isinstance(subtype, type) and issubclass(subtype, DataType):
            self.subtype = subtype()
        else:
            raise TypeError("subtype must be a DataType")

def sanitize(self, value):
        if value is None:
            return value

if not isinstance(value, (list, tuple)):
            value = [value]

value = [self.subtype.sanitize(v) for v in value]

return value

class Choice(DataType):
    def __init__(self, choices, subtype=None):
        super(Choice, self).__init__()

subtype = subtype or String()
        if isinstance(subtype, DataType):
            self.subtype = subtype
        elif isinstance(subtype, type) and issubclass(subtype, DataType):
            self.subtype = subtype()
        else:
            raise TypeError("subtype must be a DataType")

self.choices = choices

def sanitize(self, value):
        if value is None:
            return value

value = self.subtype.sanitize(value)

if value not in self.choices:
            raise DataTypeError(
                '"%s" is not one of (%s)'
                % (value, ", ".join([repr(c) for c in self.choices]))
            )

return value

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