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A question of style (finding item in list of tuples)
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Roy Smith
May 21, 2012, 8:37:29 AM5/21/12
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I've got this code in a django app:
CHOICES = [
('NONE', 'No experience required'),
('SAIL', 'Sailing experience, new to racing'),
('RACE', 'General racing experience'),
('GOOD', 'Experienced racer'),
('ROCK', 'Rock star'),
]
def experience_text(self):
for code, text in self.CHOICES:
if code == self.level:
return text
return "????"
Calling experience_text("ROCK") should return "Rock star". Annoyingly,
django handles this for you automatically inside a form, but if you also
need it in your application code, you have to roll your own.
The above code works, but it occurs to me that I could use the much
shorter:
def experience_text(self):
return dict(CHOICES).get("self.level", "???")
So, the question is, purely as a matter of readability, which would you
find easier to understand when reading some new code? Assume the list
of choices is short enough that the cost of building a temporary dict on
each call is negligible. I'm just after style and readability here.
CHOICES = [
('NONE', 'No experience required'),
('SAIL', 'Sailing experience, new to racing'),
('RACE', 'General racing experience'),
('GOOD', 'Experienced racer'),
('ROCK', 'Rock star'),
]
def experience_text(self):
for code, text in self.CHOICES:
if code == self.level:
return text
return "????"
Calling experience_text("ROCK") should return "Rock star". Annoyingly,
django handles this for you automatically inside a form, but if you also
need it in your application code, you have to roll your own.
The above code works, but it occurs to me that I could use the much
shorter:
def experience_text(self):
return dict(CHOICES).get("self.level", "???")
So, the question is, purely as a matter of readability, which would you
find easier to understand when reading some new code? Assume the list
of choices is short enough that the cost of building a temporary dict on
each call is negligible. I'm just after style and readability here.
Steven D'Aprano
May 21, 2012, 9:10:32 AM5/21/12
to
On Mon, 21 May 2012 08:37:29 -0400, Roy Smith wrote:
[...]
Rather than convert list CHOICES to a dict every time, you might convert
it to a dict *once*, then just write:
return CHOICES.get(self.level, "???")
> Assume the list
> of choices is short enough that the cost of building a temporary dict on
> each call is negligible.
Negligible or not, why bother?
Not that it really matters -- if you have a good reason for CHOICES to
remain a list, still stick with the dict lookup rather than a explicit
loop.
--
Steven
[...]
> The above code works, but it occurs to me that I could use the much
> shorter:
>
> def experience_text(self):
> return dict(CHOICES).get("self.level", "???")
>
> So, the question is, purely as a matter of readability, which would you
> find easier to understand when reading some new code?
Definitely the dictionary lookup.
> shorter:
>
> def experience_text(self):
> return dict(CHOICES).get("self.level", "???")
>
> So, the question is, purely as a matter of readability, which would you
> find easier to understand when reading some new code?
Rather than convert list CHOICES to a dict every time, you might convert
it to a dict *once*, then just write:
return CHOICES.get(self.level, "???")
> Assume the list
> of choices is short enough that the cost of building a temporary dict on
> each call is negligible.
Not that it really matters -- if you have a good reason for CHOICES to
remain a list, still stick with the dict lookup rather than a explicit
loop.
--
Steven
Jon Clements
May 21, 2012, 9:39:59 AM5/21/12
to
Failing that, if order isn't important, you can not bother with tuples and have CHOICES be a dict, then pass choices=CHOICES.iteritems() as I believe it takes any iterable, and maybe plug an ordereddict if order is important.
hth
Jon.
Roy Smith
May 21, 2012, 11:31:41 AM5/21/12
to
On Monday, May 21, 2012 9:39:59 AM UTC-4, Jon Clements wrote:
> > def experience_text(self):
> > return dict(CHOICES).get("self.level", "???")
> > def experience_text(self):
> > return dict(CHOICES).get("self.level", "???")
> Haven't used django in a while, but doesn't the model provide a get_experience_display() method which you could use...
Duh, I totally missed seeing that! Yeah, that's exactly what I want. Thanks. Hmmm, looking at the source, I see they went the dict().get() route:
def _get_FIELD_display(self, field):
value = getattr(self, field.attname)
return force_unicode(dict(field.flatchoices).get(value, value), strings_only=True)
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