what is PyCharm "simplify chained comparison"

Question

I have the following function, and PyCharm is alerting me on the elif statements about "simplify chained comparison". The code works and I am getting the object I want, just wondering about the warning and how I can make it better?

     def preferred_contacts(self):
         x = random.randint(0, 100)
         email = u'E'
         text = u'M'
         phone = u'P'
         letter = u'L'
         none = u'N'

         if x < 25:
            return email
         elif x >= 26 and x <= 50:
            return text
         elif x >= 51 and x <= 75:
            return phone
         elif x >= 76 and x <= 100:
            return letter
         else:
            return none

You could certainly remove all of the `x >=` comparisons, since by virtue of reaching `elif` it's already been shown to not match the earlier conditions — mhlester, Feb 27 '14 at 18:27
Also, you'll be glad to learn that : `elif 76 <= x <= 100:` would you what you expect it to do. — SylvainD, Feb 27 '14 at 18:29
Really you don't need the `and` ops either; `elif 26 <= x <= 50` and so on... — Drewness, Feb 27 '14 at 18:35
Also, this will never return `none`, as you've bounded `x` at 100, and 100 will return `letter`. — Silas Ray, Feb 27 '14 at 18:39
Possible duplicate of [PyCharm: "Simplify Chained Comparison"](https://stackoverflow.com/questions/26502775/pycharm-simplify-chained-comparison) — Lesmana, Dec 10 '17 at 14:35

score 1 · Accepted Answer · answered Feb 27 '14 at 18:38

1

@mhlester should get the credit for noting that you can drop the >= clauses from the conditions as they are already implicit since you are using elif. However, you could also condense things more if you wanted by putting your data in a tuple then indexing in to it.

return ('E', 'M', 'P', 'L', 'N')[x / 25] # This assumes x has an upper bound of 124 or less.

Of course, in this particular instance, you could make your life even simpler.

return random.choice(('E', 'M', 'P', 'L', 'N'))

answered Feb 27 '14 at 18:38

Silas Ray

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Thank you for this. I honestly had no idea I could just do a random choice – DarthOpto Feb 27 '14 at 20:23
Docs are your friend. ;) http://docs.python.org/2/library/random.html#random.choice – Silas Ray Feb 27 '14 at 20:38
1

Since strings are iterables, you can even just do `random.choice('EMPLN')`. – Florian Brucker Mar 19 '15 at 15:14

score 1 · Answer 2 · answered Oct 02 '18 at 09:43

Simplified chained calls for much cleaner code. See below

def preferred_contacts(self):
x = random.randint(0, 100)
email = u'E'
text = u'M'
phone = u'P'
letter = u'L'
none = u'N'

if x < 25:
    return email
elif 26 <= x <= 50: # reads as "x is between 26 and 50, inclusive
    return text
elif 51 <= x <= 75: # reads as "x is between 51 and 75, inclusive
    return phone
elif 76 <= x <= 100: # reads as "x is between 76 and 100, inclusive
    return letter
else:
    return none

what is PyCharm "simplify chained comparison"

2 Answers2