使用多态/继承将嵌套的 if 语句重构为 python 中的类

Question

网上有几个例子，其中if...else语句被使用多态/继承的构造所取代。此链接显示了类似于我想要实现的内容。我有一个嵌套结构如下：

def wishthiswouldbeobjectoriented(figuretype, randomtype):
if figuretype=='list':
# do some stuff and return a list
out = 'figure type is list'
elif figuretype=='random':
if randomtype=='all':
out = 'figure type is random and randomtype is all'
elif randomtype=='selection':
out = 'figure type is random and randomtype is selection'
return out
if __name__ == '__main__':
figuretype = 'random'
randomtype = 'selection'
print(wishthiswouldbeobjectoriented(figuretype, randomtype))

我猜应该有一种方法可以使用多态/继承将其转换为面向对象的代码。任何人都可以在python中提供一个简短的例子来演示如何将上面的代码转换为面向对象的代码吗？

Answer 1

接下来纯粹是使用继承作为调度方法的机械练习，而不是一系列显式if语句。选择不是将figure和randomtype作为参数传递给函数，而是隐式编码在类本身中。

class Figure:
def wishthiswouldbeobjectoriented(self):
pass

class FigureList(Figure):
def wishthiswouldbeobjectoriented(self):
return "figure type is list"

class FigureRandom(Figure):
pass

class FigureRandomAll(FigureRandom):
def wishthiswouldbeobjectoriented(self):
return 'figure type is random and randomtype is all'

class FigureRandomSelection(FigureRandom):
def wishthiswouldbeobjectoriented(self):
return 'figure type is random and randomtype is selection'

if __name__ == '__main__':
f = FigureRandomSelection()
print(f.wishthiswouldbeobjectoriented())

Answer 2

Commen：我如何从文本文件中知道要实例化哪个对象，

添加以下内容：

class FigureFactory:
def __new__(cls, args, **kwargs):
# Mapping Type Keywords to real Class Definition
figures = {('list',): FigureList,
('random', 'all'): FigureRandomAll,
('random', 'selection'): FigureRandomSelection
}
figure = figures.get(args)
if not figure:
figure = Figure
return figure(*kwargs['kwargs'])

扩展以下内容：

class Figure:
...
@property
def out_list(self):
return "Invalid Type"
def __str__(self):
return '{} df={}'.format(self.__class__.__name__, self.df)

class FigureRandom(Figure):
...
def __str__(self):
return '{} n_value={}'.format(super().__str__(), self.n_value)

用法：注意：无效类型list all！

if __name__ == '__main__':    
...
for cfg in [(('list',), (df,)), 
(('random', 'all'), (df, n_points)),
(('random', 'selection'), (df, n_accepted + 1)), 
(('list', 'all'), (df,))]:
figure = FigureFactory(args=cfg[0], kwargs=cfg[1])
print('{} {}'.format(figure, figure.out_list))

输出：

FigureList df=None figure type is list
FigureRandomAll df=None n_value=1 figure type is random and randomtype is all
FigureRandomSelection df=None n_value=2 figure type is random and randomtype is selection
Figure df=None Invalid Type

---

问题：在python中将嵌套的if语句重构为类

class Figure:
def __init__(self, df):
self.df = df
@property
def out_list(self):
return None

class FigureList(Figure):
def __init__(self, df):
super().__init__(df)
@property
def out_list(self):
return 'figure type is list'

class FigureRandom(Figure):
def __init__(self, df, n_value):
super().__init__(df)
self.n_value = n_value

class FigureRandomAll(FigureRandom):
def __init__(self, df, n_points):
super().__init__(df, n_points)
@property
def out_list(self):
return 'figure type is random and randomtype is all'

class FigureRandomSelection(FigureRandom):
def __init__(self, df, n_accepted):
super().__init__(df, n_accepted)
@property
def out_list(self):
return 'figure type is random and randomtype is selection'

用法：

if __name__ == '__main__':    
df = None
n_points = 1
n_accepted = 1
for figure in [FigureList(df), FigureRandomAll(df, n_points), FigureRandomSelection(df, n_accepted)]:
print('{}'.format(figure.out_list))

输出：

figure type is list
figure type is random and randomtype is all
figure type is random and randomtype is selection