Division fails when using an int variable

kylecarroll · 11-01-2019, 05:14 AM

I'm trying to get an average rating in my plugin and I keep getting a 'divide by zero' error when I do this:

Code:

 top = int(sum(rateList))
            bottom = int(len(rateList))
            averageRating = top/bottom

However, if I change the "/" to any other mathematical symbol, it works as expected. Additionally, if I remove the variables and use plain int values, it works fine. Is this a bug, or am I doing something wrong?

davidfor · 11-01-2019, 10:32 AM

What is "ratelist"? I assume it is supposed to be a list of numbers. But, with that result, I would assume it is an empty list. Have you checked that it has the values in it you expect?

theducks · 11-01-2019, 11:30 AM

When you make an Int from a small fraction, you could end up with a zero .
You really need to test for that before attempting division

DNSB · 11-01-2019, 05:40 PM

Quote:

Originally Posted by theducks

When you make an Int from a small fraction, you could end up with a zero .
You really need to test for that before attempting division

In this case, it would seem ratelist would have to have no members for the len to be set to 0. I am also wondering why the conversion to int is being done -- the len() function should be returning an int.

Perhaps a look at how ratelist is being generated and what is being returned? A few print statements to see what is actually being generated?

kylecarroll · 11-01-2019, 05:54 PM

I've tested by printing each statement len(rateList) and sum(rateList) and both give the expected values.

Additionally, I have them casted to int in that example just because that is what I had currently tried doing to ensure it was indeed an int. I've done it without the casting as well to no avail.

kylecarroll · 11-01-2019, 06:02 PM

I figured it out! The division was nested inside a for loop which was generating the rate list. So, on the first iteration, that list WAS empty. I moved it outside of the loop and worked as expected. Thanks for getting my brain turning.

theducks · 11-01-2019, 10:14 PM

Quote:

Originally Posted by kylecarroll

I figured it out! The division was nested inside a for loop which was generating the rate list. So, on the first iteration, that list WAS empty. I moved it outside of the loop and worked as expected. Thanks for getting my brain turning.

Hopefully our discussion helped.
Come to think of it, I chased one many decades ago, where I forgot to initialize the (self typing) variable. First pass, it would bomb with a 'wrong type' error

kylecarroll · 11-01-2019, 10:36 PM

The discussion definitely helped. Sometimes all it takes is bouncing your thoughts off of others to find your goofs!

11-01-2019, 05:14 AM	#1
kylecarroll Junior Member Posts: 9 Karma: 10 Join Date: Oct 2019 Device: Kindle	Division fails when using an int variable I'm trying to get an average rating in my plugin and I keep getting a 'divide by zero' error when I do this: Code: top = int(sum(rateList)) bottom = int(len(rateList)) averageRating = top/bottom However, if I change the "/" to any other mathematical symbol, it works as expected. Additionally, if I remove the variables and use plain int values, it works fine. Is this a bug, or am I doing something wrong?

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11-01-2019, 10:32 AM	#2
davidfor Grand Sorcerer Posts: 24,905 Karma: 47303824 Join Date: Jul 2011 Location: Sydney, Australia Device: Kobo:Touch,Glo, AuraH2O, GloHD,AuraONE, ClaraHD, Libra H2O; tolinoepos	What is "ratelist"? I assume it is supposed to be a list of numbers. But, with that result, I would assume it is an empty list. Have you checked that it has the values in it you expect?

11-01-2019, 11:30 AM	#3
theducks Well trained by Cats Posts: 31,343 Karma: 62025226 Join Date: Aug 2009 Location: The Central Coast of California Device: Kobo Libra2,Kobo Aura2v1, K4NT(Fixed: New Bat.), Galaxy Tab A	When you make an Int from a small fraction, you could end up with a zero . You really need to test for that before attempting division

11-01-2019, 05:54 PM	#5
kylecarroll Junior Member Posts: 9 Karma: 10 Join Date: Oct 2019 Device: Kindle	I've tested by printing each statement len(rateList) and sum(rateList) and both give the expected values. Additionally, I have them casted to int in that example just because that is what I had currently tried doing to ensure it was indeed an int. I've done it without the casting as well to no avail.

11-01-2019, 06:02 PM	#6
kylecarroll Junior Member Posts: 9 Karma: 10 Join Date: Oct 2019 Device: Kindle	I figured it out! The division was nested inside a for loop which was generating the rate list. So, on the first iteration, that list WAS empty. I moved it outside of the loop and worked as expected. Thanks for getting my brain turning.

11-01-2019, 10:36 PM	#8
kylecarroll Junior Member Posts: 9 Karma: 10 Join Date: Oct 2019 Device: Kindle	The discussion definitely helped. Sometimes all it takes is bouncing your thoughts off of others to find your goofs!

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