7

我正在用 Python 编写脚本，但遇到了一些问题：

class LightDMUser(QObject):
  def __init__(self, user):
    super(LightDMUser, self).__init__()
    self.user = user

  @pyqtProperty(QVariant)
  def background(self):      return self.user.get_background()

  @pyqtProperty(QVariant)
  def display_name(self):    return self.user.get_display_name()

  @pyqtProperty(QVariant)
  def has_messages(self):    return self.user.get_has_messages()

  @pyqtProperty(QVariant)
  def home_directory(self):  return self.user.get_home_directory()

  @pyqtProperty(QVariant)
  def image(self):           return self.user.get_image()

  @pyqtProperty(QVariant)
  def language(self):        return self.user.get_language()

  @pyqtProperty(QVariant)
  def layout(self):          return self.user.get_layout()

  @pyqtProperty(QVariant)
  def layouts(self):         return self.user.get_layouts()

  @pyqtProperty(QVariant)
  def logged_in(self):       return self.user.get_logged_in()

  @pyqtProperty(QVariant)
  def name(self):            return self.user.get_name()

  @pyqtProperty(QVariant)
  def real_name(self):       return self.user.get_real_name()

  @pyqtProperty(QVariant)
  def session(self):         return self.user.get_session()

如您所见，这段代码非常多余。我试着像这样浓缩它：

class LightDMUser(QObject):
  attributes = ['background', 'display_name', 'has_messages', 'home_directory', 'image', 'language', 'layout', 'layouts', 'logged_in', 'name', 'real_name', 'session']

  def __init__(self, user):
    super(LightDMUser, self).__init__()
    self.user = user

    for attribute in self.attributes:
      setattr(self, attribute, pyqtProperty(QVariant, getattr(self.user, 'get_' + attribute)))

然而，PyQt4 期望类方法存在于类本身，而不是实例。将setattr代码移出__init__块也不起作用，因为self没有为类定义，所以我真的不知道该怎么做。

任何人都可以看到压缩此代码的方法吗？

4

6 回答 6

5

有很多方法可以做到这一点：类装饰器、元类、Mixin。

常用辅助函数：

def set_pyqtproperties(klass, properties, proxy='user'):
    def make_prop(prop):        
        def property_(self):
            return getattr(getattr(self, proxy), 'get_' + prop)
        property_.__name__ = prop
        return property_

    if isinstance(properties, basestring):
       properties = properties.split()
    for prop in properties:
         setattr(klass, prop, pyqtProperty(QVariant, make_prop(prop)))

类装饰器

def set_properties(properties):
    def decorator(klass):
        set_pyqtproperties(klass, properties)
        return klass
    return decorator
用法 
@set_properties("display background")
class LightDMUser(QObject): pass

如果不支持类装饰器，那么您可以尝试：

class LightDMUser(QObject): 
    pass
LightDMUser = set_properties("display background")(LightDMUser)

元类

def set_properties_meta(properties):
    def meta(name, bases, attrs):
        cls = type(name, bases, attrs)
        set_pyqtproperties(cls, properties)
        return cls
    return meta
用法 
class LightDMUser(QObject):
    __metaclass__ =  set_properties_meta("display background")

注意：如果将属性列表设置为类属性，则可以重用相同的元类：

def MetaClass(name, bases, attrs):
    cls = type(name, bases, attrs)
    set_pyqtproperties(cls, attrs.get('properties', ''))
    return cls

class LightDMUser(QObject):
    properties = "display background"
    __metaclass__ = MetaClass

您也可以attrs直接操作：attrs[name] = value在调用type()而不是setattr(cls, name, value).

以上假设QObject.__class__ is type.

米信

def properties_mixin(classname, properties):
    #note: create a new class by whatever means necessary
    # e.g., even using exec() as namedtuple does
    # http://hg.python.org/cpython/file/3.2/Lib/collections.py#l235

    # reuse class decorator here
    return set_properties(properties)(type(classname, (), {}))
用法 
PropertiesMixin = properties_mixin('PropertiesMixin', 'display background')
class LightDMUser(PropertiesMixin, QObject): pass

我没有尝试过任何一个。此处的代码显示了实现该功能可能需要的代码数量和类型。

于 2012-08-12T12:08:21.800 回答
2

You could attach these methods from еру outside of the class definition:

class LightDMUser(QObject):

  def __init__(self, user):
    super(LightDMUser, self).__init__()
    self.user = user

The simplest way is to create a closure for each property, override its __name__ (just for case if @pyqtProperty needs it) and to bind it to the class:

for attribute in [
        'background',
        'display_name',
        'has_messages',
        'home_directory',
        'image',
        'language',
        'layout',
        'layouts',
        'logged_in',
        'name',
        'real_name',
        'session'
      ]:

  def delegating(self):
    return getattr(self.user, 'get_' + attribute)()

  delegating.__name__ = attribute
  delegating = pyqtProperty(QVariant)(delegating)

  setattr(LightDMUser, attribute, delegating)
于 2012-08-12T11:28:55.003 回答
1

如果您将循环移出类并创建一个闭包来保存每个属性名称，我很确定这可以工作：

class LightDMUser(QObject):
    attributes = ['background', 'display_name', 'has_messages',
                  'home_directory', 'image', 'language', 'layout',
                  'layouts', 'logged_in', 'name', 'real_name', 'session']

    def __init__(self, user):
        super(LightDMUser, self).__init__()
        self.user = user

for attribute in LightDMUser.attributes:
    closure = lambda self, attribute=attribute : getattr(self.user,
                                                         'get_' + attribute)()
    setattr(LightDMUser, attribute, pyqtProperty(QVariant, closure))

我没有使用您正在处理的基于 QT 的实际类对此进行测试，但是使用常规 Pythonproperty实例的更简单版本可以完美运行。我也不确定这是一个好主意，因为如果您还不熟悉它，就很难弄清楚发生了什么。

于 2012-08-12T10:56:57.737 回答
1

我不相信我喜欢这个，但它是一个可能的选择，不是太难理解，并且不需要getattr's... 以下可以有点像宏使用 - 但可能需要调整.. . （例如，从以 get 开头的类定义或从现有对象等中获取 funcs ）还可以在其中添加一个repr来描述它是一个支持类，用于与用户对象或其他任何属性进行接口... )

def get_properties(name, funcs):
    get_text = """
class {name}(QObject):
""".format(name=name)
    for func in funcs:
        get_text += (
              "\n\t@pyqtProperty(QVariant)\n"
              "\tdef {func}(self): return self.user.get_{func}()\n"
              ).format(func=func)

    print get_text # this should be exec...

>>> get_properties('UserProperties', ['display', 'background'])

class UserProperties(QObject):

    @pyqtProperty(QVariant)
    def display(self): return self.user.get_display()

    @pyqtProperty(QVariant)
    def background(self): return self.user.get_background()

执行该命令后，您可以将主类编写为：

class LightDMUser(QObject, UserProperties):
    def __init__(self, user):
        super(LightDMUser, self).__init__()
        self.user = user
于 2012-08-12T11:10:13.593 回答
1

我为 Python 3 测试了下面的解决方案。它使用 metaclass 关键字

# A bit of scaffolding

def pyqtProperty(cls, method):
    return method

class QObject:
    pass

class QVariant:
    pass

class User:
    def __init__(self, name="No Name"):
        self.name = name
    def get_background(self):
        return self.name
    def get_display_name(self):
        return self.name
    def get_has_messages(self):
        return self.name
    def get_home_directory(self):
        return self.name
    def get_image(self):
        return self.name
    def get_language(self):
        return self.name
    def get_layout(self):
        return self.name
    def get_layouts(self):
        return self.name
    def get_logged_in(self):
        return self.name
    def get_name(self):
        return self.name
    def get_real_name(self):
        return self.name
    def get_session(self):
        return self.name

# The Meta Class
class MetaLightDMUser(type):
    @classmethod
    def __prepare__(cls, name, baseClasses):
        classdict = {}
        for attribute in ['background', 'display_name', 'has_messages', 'home_directory', 'image', 'language', 'layout', 'layouts', 'logged_in', 'name', 'real_name', 'session']:
            classdict[attribute] = eval("lambda self: pyqtProperty(QVariant, getattr(self.user, 'get_" + attribute +"'))()")
        return classdict

    def __new__(cls, name, baseClasses, classdict):
        return type.__new__(cls, name, baseClasses, classdict)

# The class itself
class LightDMUser(QObject, metaclass = MetaLightDMUser): 
    def __init__(self, user):
        super(LightDMUser, self).__init__()
        self.user = user

或者我可以像这样创建classdict条目

classdict[attribute] = lambda self, attr=attribute: pyqtProperty(QVariant, getattr(self.user, 'get_' + attr))()

但这提出了一个 attr 论点。有了eval()我们的核心这个论点

我们也可以使用functools.partial：

classdict[attribute] = functools.partial(lambda self, attr: pyqtProperty(QVariant, getattr(self.user, 'get_' + attr))(), attr=attribute)

但随后的调用必须是u.method(u)。它不可能是u.method()

该调用LightDMUser.method(u)适用于所有 3 个实现

问候

于 2012-08-12T15:21:02.957 回答
0

使用元类或类装饰器来减少 pyqtProperty 的样板文件是很棘手的，但这是我们刚刚开始工作的一个起点。我想，不利的一面是您不再可以使用@decorator 语法，但在这种情况下，似乎将其合并到一行代码中更可取。

您可以将其设置为调用您的用户对象而不仅仅是 self，或者您可以为 LightDMUser 实现自定义 getattr 行为，该行为将自动调用 self.user。

from PyQt4.QtCore import pyqtProperty
from PyQt4.QtGui import QWidget, QColor
from functools import partial

def pyqtPropertyInit(name, default):
    def _getattrDefault(default, self, attrName):
        try:
            value = getattr(self, attrName)
        except AttributeError:
            setattr(self, attrName, default)
            return default
        return value
    ga = partial(_getattrDefault, default)
    return pyqtProperty(
        default.__class__,
        fget=(lambda s: ga(s, name)),
        fset=(lambda s, v: setattr(s, name, v)),
    )

class TestClass(QWidget):
    def __init__(self, *args, **kwargs):
        super(TestClass, self).__init__(*args, **kwargs)

    stdoutColor = pyqtPropertyInit('_stdoutColor', QColor(0, 0, 255))
    pyForegroundColor = pyqtPropertyInit('_pyForegroundColor', QColor(0, 0, 255))
于 2015-03-27T01:47:05.217 回答