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Reputation: 965

Best practice for refactoring a python function to return a tuple, instead of a single variable?

I am refactoring a python function in a large codebase. Currently, it looks like:

def GetEvents(file_path):

    ...

    return events #a list of Event objects

A bunch of code depends on this function returning a list object already. However, I want to refactor it so it returns:

def GetEvents(file_path):

    ...

    return (events, event_header)

Where event_header is a little description of this group of events. However, this will badly break all code that currently expects a list, not a tuple to be returned. In any other language, I would pass the event_header by reference, but I do not think I can do that in Python. I could also declare another function, GetEventsAndHeader(), but that awkwardly duplicates functionality.

Suggestions?

Upvotes: 2

Views: 983

Answers (3)

dorian
dorian

Reputation: 6272

If you don't absolutely need to return a tuple, just add an attribute to your returned list:

class EventList(list):
    pass


def GetEvents(file_path):

    ...

    events = EventList(events)
    events.event_header = some_header
    return events

Upvotes: 6

Marcin
Marcin

Reputation: 49826

Well, as noted, if this takes no arguments, then it probably shouldn't be a function. I'd add that it's probably part of an object, and if not, it should be.

That way, you can have:

class EventGroup(object):

     def GetEvents(): # note camelcase is not pep8 compliant
         return dat_list


     def EventGroupInfo():
         return some_info

     def fact_about_events1():
         return fact1

     def fact_about_events2():
         return fact2

I've used no-argument methods to parallel your code, but I don't necessarily recommend it.

An alternative design choice would be to return an object which respects the full list protocol, and carries metadata about the group of events also.

Upvotes: 0

Martijn Pieters
Martijn Pieters

Reputation: 1121724

Rename the function to GetEventsAndHeader(), and add a new function GetEvents():

def GetEvents(*args, **kw):
    return GetEventsAndHeader(*args, **kw)[0]

or just bite the bullet and update all code that calls GetEvents() and adjust that code to either use the returnvalue indexed to [0] or make use of the headers as well.

Upvotes: 8

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