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Messenger/Data Transfer Object

Метки: python

The Messenger or Data Transfer Object is a way to pass a clump of information around. The most typical place for this is in return values from functions, where tuples or dictionaries are often used. However, those rely on indexing; in the case of tuples this requires the consumer to keep track of numerical order, and in the case of a dict you must use the d["name"] syntax which can be slightly less desireable.

A Messenger is simply an object with attributes corresponding to the names of the data you want to pass around or return:

# Messenger/MessengerIdiom.py

class Messenger:
    def __init__(self, **kwargs):
        self.__dict__ = kwargs

m = Messenger(info="some information", b=['a', 'list'])
m.more = 11
print m.info, m.b, m.more

The trick here is that the __dict__ for the object is just assigned to the dict that is automatically created by the **kwargs argument.

Although one could easily create a Messenger class and put it into a library and import it, there are so few lines to describe it that it usually makes more sense to just define it in-place whenever you need it – it is probably easier for the reader to follow, as well.