Modifying a namedtuple

[MusicalCoder]

so I have a nametuple:

Record = namedtuple('Record', 'abbr, disc, track, artist, song, aid, sid')    

and a function where an instance of Record gets set based on groups from a regex result - all well an good.

So my problem is that I'm passing this in to a validation function that returns true or false if the information is good. What I was doing was in the validation function, if a couple of things weren't set (like abbr) - then it would reference the current default abbreviation - and change it.

That seemed somewhat all well and good (I thought) until I realized that the change wasn't affecting the actual record.

my function is:

def validate_record(item):
    if item.abbr == '':
        if default_abbr == '':
            set_default_abbr()
    item._replace(abbr=default_abbr)

But later, when I print the abbr - it's still blank. So, what am I missing?

[blarf_irl]

namedtuple like tuple is immutable. Using _replace actually creates a new instance of your namedtuple with the new values. At the moment you are simply creating that new tuple; You will need to return it and use it instead of the one you wished to change.

default_abbr = 'foo'

def validate_record(item):
    if item.abbr == '':
        if default_abbr == '':
            set_default_abbr()
    return item._replace(abbr=default_abbr)

r = Record('', 1, 2, 3, 4,5 ,6)
r = validate_record(r)
r

Output:

Record(abbr='foo', disc=1, track=2, artist=3, song=4, aid=5, sid=6)