在Python 3中的类方法中实现宏

Question

I have the following:

class ComplicatedClass(object):
    def _init__(self):
        self.useful_member = ...

    def method(self):
        M = self.useful_member
        ...

    def method2(self):
        M = self.useful_member
        ...

    def method3(self):
        M = self.useful_member
        ...

I am using the useful member a lot in various methods, so instead of writing the long and cumbersome self.useful_member each time, I am assigning it to the short variable name M .

Is there a way to avoid re-doing M = self.useful_member for each method?

Answer 1

I believe you are looking for something like

def quick_assignment(varName, varValue):
    def decorator(func):
        def wrapped_method(self, *args, **kwargs):
            func.__globals__[varName] = eval(varValue)
            return func(self, *args, **kwargs)
        return wrapped_method
    return decorator

def for_all_methods(decorator):
    def decorate(cls):
        for attr in cls.__dict__: # there's propably a better way to do this
            if callable(getattr(cls, attr)) and attr[:2] != '__':
                setattr(cls, attr, decorator(getattr(cls, attr)))
        return cls
    return decorate

@for_all_methods(quick_assignment('M', 'self.useful_member'))
class ComplicatedClass(object):
    def __init__(self):
      self.useful_member = 6

    def method(self):
        print(M) # Prints 6

However, as Aran-Fey suggests below, this is not ideal, but it answers your question.