Python中的动态/运行时方法创建(代码生成)

问题描述

我需要在运行时为方法生成代码.能够运行任意代码并具有文档字符串非常重要.

I need to generate code for a method at runtime. It's important to be able to run arbitrary code and have a docstring.

我想出了一个结合了exec和setattr的解决方案，这是一个虚拟的示例:

I came up with a solution combining exec and setattr, here's a dummy example:

class Viking(object):
    def __init__(self):
        code = '''
            def dynamo(self, arg):
                """ dynamo's a dynamic method!
                """
                self.weight += 1
                return arg * self.weight
            '''
        self.weight = 50

        d = {}
        exec code.strip() in d
        setattr(self.__class__, 'dynamo', d['dynamo'])


if __name__ == "__main__":
    v = Viking()
    print v.dynamo(10)
    print v.dynamo(10)
    print v.dynamo.__doc__

是否有更好/更安全/更惯用的方式获得相同的结果?

Is there a better / safer / more idiomatic way of achieving the same result?

推荐答案

基于Theran的代码，但将其扩展到类的方法上:

Based on Theran's code, but extending it to methods on classes:

class Dynamo(object):
    pass

def add_dynamo(cls,i):
    def innerdynamo(self):
        print "in dynamo %d" % i
    innerdynamo.__doc__ = "docstring for dynamo%d" % i
    innerdynamo.__name__ = "dynamo%d" % i
    setattr(cls,innerdynamo.__name__,innerdynamo)

for i in range(2):
    add_dynamo(Dynamo, i)

d=Dynamo()
d.dynamo0()
d.dynamo1()

应打印:

in dynamo 0
in dynamo 1

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