如何调用在文本变量中具有名称的类构造函数？ [蟒蛇] [英] How to call class constructor having its name in text variable? [Python]

问题描述

假设我们定义了一些类，并且这些类在全局名称空间中可用。例如：

Let's assume we have some classes defined and available in global namespace. In example:

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

class Vector:
    def __init__(self, alpha, r):
        self.x = r * cos(alpha)
        self.y = r * sin(alpha)

# and many others...

操作方法：

class_name = 'Point'
x = 14.361
y = -8.100
code_str = 'class_object = ' + class_name + '(' + str(x) + ', ' + str(y) + ')'

exec code_str  # That evaluates to: "class_object = Point(14.361, -8.100)"

print class_object.x, class_object.y

而不使用危险的执行程序？

without using the dangerous exec?

PS。如果有人问，我打算从一些txt或json文件中加载数据。

PS. I'm intending to load the data from some txt or json file if anyone asks.

推荐答案

如果已定义或导入了该类在同一模块中，您可以使用类似以下内容的东西：

If the class is defined or imported in the same module, you could use something like :

globals()[class_name](x, y)

如果要处理的类很多，最好使用字典来存储它们，键是名称，值是该类，

if you have many classes to handle, you should better use a dictionnary to store them, key is the name, value is the class,

然后您可以使用以下命令来调用它：

then you can call it with :

my_classes = {'Point' : Point, 'Point2' : Point2}

class_name = 'Point'
x = 14.361
y = -8.100
my_classes[class_name](x, y)

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