A question of style (finding item in list of tuples)
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.
--
http://mail.python.org/mailman/listinfo/python-list
Re: A question of style (finding item in list of tuples)
On Mon, May 21, 2012 at 10:37 PM, Roy Smith r...@panix.com wrote: 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. Is there a reason not to keep the dictionary around? That would surely be the most logical thing to do. (With, of course, no quotes around self.level.) But out of your two options, I'd go with the loop. It's clear what you're doing and doesn't fiddle around with multiple translations. Chris Angelico -- http://mail.python.org/mailman/listinfo/python-list
Re: A question of style (finding item in list of tuples)
On Mon, 21 May 2012 08:37:29 -0400, Roy Smith wrote: [...] 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. 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 -- http://mail.python.org/mailman/listinfo/python-list
Re: A question of style (finding item in list of tuples)
One suggestion is to construct the dictionary first:
CHOICES = dict(
NONE = 'No experience required',
SAIL = 'Sailing experience, new to racing',
RACE = 'General racing experience',
GOOD = 'Experienced racer',
ROCK = 'Rock star'
)
def experience_text(self):
try:
return CHOICES[self]
except:
return
On 05/21/2012 07:37 AM, Roy Smith wrote:
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.
--
http://mail.python.org/mailman/listinfo/python-list
Re: A question of style (finding item in list of tuples)
On 05/21/12 08:10, Steven D'Aprano wrote: On Mon, 21 May 2012 08:37:29 -0400, Roy Smith wrote: [...] 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. 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, ???) While I back Steven's suggestion, I'd keep *both* around. The dictionary isn't inherently ordered, so presenting it to the user may come out with a differing orders depending on how code gets hit. So I'd do CHOICES = [ (NONE, No experience required), ... ] CHOICE_DICT = dict(CHOICES) once at setup, and then use Steven's suggestion of return CHOICES_DICT.get(self.level, ???) then you get the best of both worlds: You can specify the order for presentation using CHOICES, and get O(1) lookups and defaulting via CHOICE_DICT. -tkc -- http://mail.python.org/mailman/listinfo/python-list
Re: A question of style (finding item in list of tuples)
On Monday, 21 May 2012 13:37:29 UTC+1, Roy Smith wrote:
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.
Haven't used django in a while, but doesn't the model provide a
get_experience_display() method which you could use...
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.
--
http://mail.python.org/mailman/listinfo/python-list
Re: A question of style (finding item in list of tuples)
On Monday, May 21, 2012 9:39:59 AM UTC-4, Jon Clements wrote: 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) -- http://mail.python.org/mailman/listinfo/python-list
