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@c-bata
Last active September 13, 2015 02:22
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Pythonのメタクラスを使ってフィールドが定義された順番を保持する
import itertools
class _BaseValidator(object):
_counter = itertools.count()
def __new__(cls, *args, **kw):
validator = object.__new__(cls)
validator._order = next(cls._counter)
return validator
class _ValidatorMeta(type):
validators = []
def __init__(cls, name, bases, clsattrs):
for name, value in clsattrs.items():
if isinstance(value, _BaseValidator):
delattr(cls, name)
if not value.name:
value.name = name
cls.validators.append((value._order, value))
cls.validators.sort()
BaseValidator = _ValidatorMeta(
'BaseValidator',
(_BaseValidator,),
{}
)
class SampleDataFrame(object):
id = BaseValidator()
name = BaseValidator()
age = BaseValidator()
if __name__ == '__main__':
hoge = SampleDataFrame()
print("id: ", hoge.id._order)
print("name: ", hoge.name._order)
print("age: ", hoge.age._order)
# $ python3 metaclasses_sample.py
# id: 0
# name: 1
# age: 2
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