Cannot call method unless its global from a class

Question

Hi I am new to Disco and integrating existing code to it. Is Disco capable to call map/reduce function as a function within a class instead of global function? The following code might explain more clearly.

class Segmenter(object):
    def map_fun(line, params):
        ....
    def reduce_fun(iter, params):
        ....
    def disco_mp(self):
        job = Job().run(input=["raw://word_to_segment_......"],
                        map=map_fun,
                        reduce=reduce_fun)
        ...

The result of execution is

NameError: global name 'map_fun' is not defined

But if I change map_fun, reduce_fun into global function, it would work fine as expected. However I still have to find a way to make it work as class functions, is there any way to do it ?

Thanks,

Chandler

Answer 1

You need static method, you can do this with decorator:

class Segmenter(Job):
    map = staticmethod(map_fun)
    reduce = staticmethod(reduce_fun)

    @staticmethod
    def map_fun(line, params):
        ....

    @staticmethod
    def reduce_fun(iter, params):
        ....

    def disco_mp(self):
        job = self.run(input=["raw://word_to_segment_......"])

Note that you will not have access to self in both map_fun and reduce_fun, and this is why params exists. Also note that Job.run is now self.run and Segmenter extends Job.

Answer 2

It looks like you want to use self.map_fun and self.reduce_fun. Methods of objects can't be accessed by their bare names in Python; you have to use self. You will also need to provide a self argument to those methods. You should read the Python tutorial to familiarize yourself with the basics of classes and methods in Python.

(Also, why is the title of your question unrelated to the actual question?)