Question

我创建了一些Python类作为多变量数据结构，然后用于各种任务。在某些情况下，我喜欢使用各种值集填充类。默认参数filename＆＃34; ho2.defaults＆＃34;看起来像这样：

name = 'ho2'
mass_option = 'h1o16'
permutation = 'odd'
parity = 'odd'
j_total = 10
lr = 40
br = 60
jmax = 60
mass_lr = 14578.471659
mass_br = 1781.041591
length_lr = ( 1.0, 11.0, 2.65 )
length_br = ( 0.0, 11.0, 2.46 )
use_spline = True
energy_units = 'au'
pes_zpe = -7.407998138300982E-2
pes_cutoff = 0.293994

目前，我通过从文件中读取所需的键，值对来创建字典，现在我想要一个＆＃34; pythonic＆＃34;使这些字典键的方法是类实例变量名，即

# Instantiate Molecule Class
molecule = Molecule()

# Create Dictionary of default values
default_dict = read_dict_from_file(filename)

# Set populate class instance variables with dictionary values
for key,value in default_dict:
    molecule.key = value

所以Class的实例变量＆＃34; molecule.name＆＃34;可以使用字典键，值对设置。我可以手动完成这项工作，但我确信有更好的方法可以循环使用它。实际上，字典可能很大，我宁愿允许用户选择他们想要填充的值，因此字典可能会改变。我在这里缺少什么？

Answer 1

简单的方法是：

vars(molecule).update(default_dict)

这会破坏任何预先存在的属性。对于更精细的方法，尝试：

for name, value in default_dict.items():
    if not hasattr(molecule, name):
        setattr(molecule, name value)

Answer 2

您可以使用setattr：setattr(molecule, key, value)

Answer 3

我反转逻辑，以便对象动态回答问题：

class Settings(object):
    ATTRS = {'foo', 'bar'}

    def __init__(self, defaults):
        self.__dict__['data'] = defaults.copy()

    def __getattr__(self, key):
        if key not in self.ATTRS or key not in self.data:
            raise AttributeError("'{}' object has no attribute '{}'".format(
                self.__class__.__name__, key))
        return self.data[key]

    def __setattr__(self, key, value):
        self.data[key] = value


s = Settings({'a': 'b', 'foo': 'foo!', 'spam': 'eggs'})
print s.foo

try:
    print s.spam
except AttributeError:
    pass
else:
    raise AssertionError("That should have failed because 'spam' isn't in Settings.ATTRS")

try:
    print s.bar
except AttributeError:
    pass
else:
    raise AssertionError("That should have failed because 'bar' wasn't passed in")

class Molecule(settings):
    ATTRS = {'name', 'mass_option', ...}

molecule = Molecule(default_dict)

如何使用字典键，值对设置类实例属性＆＃34; pythonic＆＃34; ly？

3 个答案: