Design patterns 工厂方法分解为模块

我一直在看一个简单的工厂示例

from __future__ import generators
import random

class Shape(object):
    # Create based on class name:
    def factory(type):
        #return eval(type + "()")
        if type == "Circle": return Circle()
        if type == "Square": return Square()
        assert 0, "Bad shape creation: " + type
    factory = staticmethod(factory)

class Circle(Shape):
    def draw(self): print("Circle.draw")
    def erase(self): print("Circle.erase")

class Square(Shape):
    def draw(self): print("Square.draw")
    def erase(self): print("Square.erase")

# Generate shape name strings:
def shapeNameGen(n):
    types = Shape.__subclasses__()
    for i in range(n):
        yield random.choice(types).__name__

shapes = \
  [ Shape.factory(i) for i in shapeNameGen(7)]

for shape in shapes:
    shape.draw()
    shape.erase()

并试图将其分为不同的文件

main.py 圆圈.py square.py 当运行它时，我得到 ImportError:无法导入名称“Circle”

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因此，尽管当所有类都在同一个模块中时，该示例仍然有效，但从分离的模块导入它们时似乎存在问题。有什么想法吗？

我刚刚将factory类（Shape）与其他形状继承自的基类分开，这似乎起到了作用

from __future__ import generators
import random

from factory.shapes.circle import Circle
from factory.shapes.sqaure import Square


class Shape(object):
    # Create based on class name:
    def factory(type):
        #return eval(type + "()")
        if type == "Circle": return Circle()
        if type == "Square": return Square()
        assert 0, "Bad shape creation: " + type
    factory = staticmethod(factory)


# Generate shape name strings:
def shapeNameGen(n):
    types = Shape.__subclasses__()
    for i in range(n):
        yield random.choice(types).__name__

shapes = \
  [ Shape.factory(i) for i in shapeNameGen(7)]

for shape in shapes:
    shape.draw()
    shape.erase()

from __future__ import generators
import random

from factory.main import Shape

class Circle(Shape):
    def draw(self): print("Circle.draw")
    def erase(self): print("Circle.erase")

from __future__ import generators
import random

from factory.main import Shape

class Square(Shape):
    def draw(self): print("Square.draw")
    def erase(self): print("Square.erase")