按照他们的声明顺序通过班级成员进行迭代

Question

编写一个将类映射到简单表视图的GUI库时,我遇到了这个问题.某个类型=列的每个类成员以及列的顺序都很重要.但...

class Person(object):

    name = None
    date_of_birth = None
    nationality = None
    gender = None
    address = None
    comment = None


for member in Person.__dict__.iteritems():
    if not member[1]:
        print member[0]

输出:

comment
date_of_birth
name
address
gender
nationality
...

呃,奥得河搞得一团糟......想要的输出:

name
date_of_birth
nationality
gender
address
comment

有没有办法在不保留额外OrderedDict()列的情况下完成？

Answer 1

在Python3中,可以通过使用PEP3115来允许您在构造类时覆盖元类中的dict类型(例如,使用跟踪插入顺序的OrderedDict).以下是此方法的实现:

class OrderedMeta(type):
    @classmethod
    def __prepare__(metacls, name, bases): 
        return OrderedDict()

    def __new__(cls, name, bases, clsdict):
        c = type.__new__(cls, name, bases, clsdict)
        c._orderedKeys = clsdict.keys()
        return c

class Person(metaclass=OrderedMeta):
    name = None
    date_of_birth = None
    nationality = None
    gender = None
    address = None
    comment = None

for member in Person._orderedKeys:
    if not getattr(Person, member):
        print(member)

在Python2中,它更加棘手.它可以用一些相当粗暴的东西来实现,比如内省源代码,并从AST中确定定义顺序,但这可能比它的价值更麻烦.