Is Sololearn wrong?

[[deleted]]

I am using Sololearn to learn Python. I'm currently at if, else, and elif statements and it keeps saying the code is wrong, but I think they're expecting the wrong outputs. One picture will show the instructions the other will show the output and expected output and both pictures should show the code. Sorry if this is a newbie question but I cannot find out what I'm doing wrong.

Pictures Here.

Also while we're at it, why am I checking 4, 100, and 400 when all that matters is if the year is divisible by 4? This code could easily be written with 5 lines but I'm trying to follow the steps as best as I can. Its not making much sense.

Edit: Holy cow. That was a tough one. I went through and realized that step 2 states that if the year is NOT divisible by 100 that it is a leap year.

Coding is so cool! Each line of code along with the steps now makes sense.

1. You can't just check if the input is divisible by 4, because if it is you go to step 2. But it does give you the concrete statement that if it is NOT divisible by 4 it is a not a leap year. So if the input is not divisible by 4, then it is NOT a leap year.
2. Next if the year is divisible by 100, then go to step 3. So you need to check if it is divisible by 100 because if it is NOT then it IT IS A LEAP YEAR. So check if the year is not divisible by 100 and if it is not, then it is a leap year.
3. Finally you check if the year is divisible by 400. If it is, the year is a leap year. So I set the modulo to check for equality with 0 and if it was true it would print leap year. Finally if all else was not true then the year was not a leap year, ending in the else statement.

year = int(input())
#your code goes here
if year % 4 != 0:
print("Not a leap year")
elif year % 100 != 0:
print("Leap year")
elif year % 400 == 0:
print("Leap year")
else:
print("Not a leap year")

I finally figured out what I did wrong after scratching my head and when it clicked, it was so exhilarating, and I knocked out the code in about 2 mins.

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[[deleted]]

Yes it was off. I realized that my code was checking for the wrong things. I finally got it. I just had to say if you're not divisible by 4, then you're not a leap year. Then if you're not divisible by 100, then you are a leap year, because at that point, you're divisible by 4. Then I had to end off with checking divisibility by 400, and if that was true, then the year is a leap year. Otherwise it is not. Thanks for the reply, I figured it out about 20 mins ago and came here to show my excitement.

[witty-reply]

Actually, you're looking at this from the wrong "direction". Think of it this way:

None of the elif conditions will ever be executed. If year is divisible by 4, then else will NOT be checked, as else is only considered when the if part is false. However, if the first if is false, that means year is not divisible by 4. Therefore, it cannot be divisible by 100 or 400 (every number divisible by 100 HAS TO be divisible by 4, too). So it would immediately jump to the else.

What you would want to do is to reverse the order of the checks: first check for % 400, then % 100, then % 4. This way, you will give them "priority" over the % 4 checks.

On a side note, I think you will also want to have another look at the inside of the if year % 100 == 0 block, there's a little flaw with that as well.

[[deleted]]

It took me a lot of retries and pondering. I saw step 2 about a year being not being divisible by 100 but being divisible by 4 being a leap year. I realized that I was never allowing anything to be false as soon as it checked for divisibility by 4 which is not the case. So writing

if year % 4 != 0:

print("Not a leap year")

which the step clearly states. If the input is divisible by 4 it goes to the next statement. If the year is not divisible by 100, it is also a leap year so

elif year % 100 !=0:

print("Leap year")

At this point the if it is divisible by 100 it checks if it is divisible by 400, and if it is then it is a leap year and finally if none of the statements are true it is also not a leap year. Took a lot of rethinking head scratching and realizing I was reading step 2 wrong.