Write a function
kpagcha For the learners: you should know that doing something like the setup for this challenge inclines you to do is a bad practice. Never do the following:
def f(): if condition: return True else: return False
This is just dumb. You are returning a boolean, so why even use if blocks in the first place? The correct what of doing this would be:
def f(): return condition
Because this already evaluates as a boolean.
So in this challenge, forget about ifs and elses, and that leap variable, and just do the following:
def is_leap(year): return year % 4 == 0 and (year % 400 == 0 or year % 100 != 0)
Don't be redundant, be DRY.
dujincong_dufe How does the "return year%4==0..." sentence know what you are returning is a boolean? Is that defined by "def is_leap"? Thank you
kpagcha because all expressions used in that return statement evaluate to booleans
IndianRockPython thanx
_Kalpesh_ thanks brother
Krishnasaivamsi sir,can you give a clear description about return statements
srious Check out python truthiness
ajayi some of us do that for clarity sake for those who may have a hard time processing what is going on.
darshanjadav97 This is what i did.
def is_leap(year): if year%4==0: return True elif year%100==0: return False elif year%400==0: return True
Thanks for explaining
arpita0116 the first if statement if year%4==0: return True this will give true for 1900 year also but that it is not true
a_kamal_89 You can just reverse the order and it will be fine.
ryoutausami_pyd1 Took a few tries before I understood the conditions but I got it!
Here's my solution:
if year % 4 == 0: if year % 100 != 0: leap = True elif year % 400 == 0: leap = True return leaphhelzer That wound up failing two test cases.
Krishnasaivamsi how can you return heap without any function
bjohnston370 You can write it without parentheses like this:
def is_leap(year): return year % 4 == 0 and year % 100 != 0 or year % 400 == 0
amitrajitbose9 Adding parenthesis increases readability. I might be wrong though!
def is_leap(y): return ((y%4==0)and(y%100!=0)or(y%400==0))
karthik_bharadh1 what is the logic of this.....man!!!!
ingoglia But then how does python know which one you mean: 1.y%4 AND y%100, or y%400
2.y%4, and y%100 OR y%400?
That's like saying these sentences state the same thing: 1.I will eat pie and roaches, or I will eat pasta.
2.I will eat pie, and either I will eat roaches or pasta.
Am I missing something?
jrmioduszewski Just like there is order of operations for mathematical operators, there is precedence for Python operators. AND has higher precedence than OR, so it is evaluated first.
rfstahl Order of precedence: NOT > AND > OR
ujezidonye Thanks for this. I was having issues with If/ else statements.
valanukonda1999 plss explain this a bit clear how return works their
Krishnasaivamsi can you please explain the code.
sri_sam229 good one man.you seem to have pretty good understanding of python PEP.
zusammen why parenthesis are required and we get error without them??
codeharrier Associativity.
'a and b or c' reads like '(a and b) or c' to the interpreter.
'a and b' is only true every 400 years.
c is true every year except those divisible by 100, so you're marking only 3 years out of every 400 as non-leap years.
hamzabouabid7 if** year % 4 == 0 and (year % 400 == 0 or year % 100 != 0)** is true the how the true boolean is affected to leap variable since we didn't you didn't make leap=something? I hope you get the idea
chadwalt this is nice. it avoids repetition. Thanks alot.
intenseCtraining learners need to code like this imo. I use some of these programs with my classes and they simply dont understand any inline return equation, hell some of them dont even return values properly
scotmatson I agree, the multiple return statements are a tad heavy and go against DRY coding practices. However, your recommended solution also sacrifices readability, which IMO is more important than trying to massage your code into a single statement.
Be succinct but be readable. Let your bundlers handle the optimizations.
dhinastallion [deleted]
sam_fold Your answer isn't really very clean code though. So while it works, it isn't very readable, which IMO is incredibly important.
abhishekreddy041 IMO means..?
hhelzer IMO = "in my opinion"
also there's
IMHO = "in my humble opinion" (which is often not very humble at all)
abhishekreddy041 thank u
Muttnstuff Thanks that explained it so clearly
Zawaldo Makes perfect sense, thank you very much for your explanation!
Adivareyhanptr can you explain why you use the 'or' operator instead of 'and' for the 'year%100 != 0'? i still don't get it. thank you
wanglei_okay I like your func very much
himanshu_chauhan That's way shorter than my if and else loop's. Thanks.
ftakelait Hi @kpagcha,
Thanks for your detail explanation for this problem. Could you please explaine to me the relationship of your answer and the problem context, please? Because I didn't understand well the answer.
I want to unerstand how did you formulated these steps in this form you had programmed
In the Gregorian calendar three criteria must be taken into account to identify leap years:
1. The year can be evenly divided by 4; 2. If the year can be evenly divided by 100, it is NOT a leap year, unless; 3. The year is also evenly divisible by 400. Then it is a leap year
Thanks for advance. Fouzi
gaurav_sonkusle very effective buddy.... thnk u
beckwithdylan if you want to reduce redundancy, why not also return the bool of the comparisons to avoid explicitly checking for zero equivalency..
def is_leap(year): return bool(not year % 4 and (year % 100 or not year % 400))
irregardless.. you deserve an upvote
Anaximandrake Your solution is certainly the most elegant, but when the user is first presented with the problem in the coding box, the return command has already been given the object 'year' and we are given a #Write your logic here note above it. So it's at least forgivable for some of us to construct multiple 'if' blocks to solve it, wouldn't you agree?
sachinsavita95 it is not passing all the test cases?
Veerubhotla thanks :D
zpf7879 Might be clearer:
def is_leap(year): return year % 400 == 0 or year % 4 == 0 and year % 100 != 0
guardadopatrici1 Hi just a question about parenthesis placement why does placing a parenthesis like below year % 4 == 0 and (year % 400 == 0 or year % 100 != 0) is correct code versus not placing parenthesis at all or writting it like ((y%4==0)and(y%100!=0)or(y%400==0)) results in error
JayPatel2810 thanks for advice, keep commenting :)
mayank_sept92 Hi, thanks for the shorter approach but, what about the condition-- 1900<= year <=10**5
aayushbis Thank you sir for the advice.
moukhtari The calendar builtin module has a function isleap() that returns True if the year is leap, otherwise it returns False
import calendar def is_leap(year): return calendar.isleap(year)
michaelhuynhquoc What I just learnt from you: don't re-invent the wheel :D
super_geek true af
ajayi haha, you are the boss.
cssd1983 Amazing
flmmartins The problem's explanation is not clear. I am not an english speaker and the bullet points were not clear enough for me.
Can that be improved?
Suggested explanation is bellow:
In the Gregorian calendar three criteria must be taken into account to identify leap years
The year can be evenly divided by 4; If the year can be evenly divided by 100, then it is not a leap year The year is also evenly divisible by 400 then it is a leap year.veganXedge i agree. maybe this has something to do with my math skil level but, i couldn't understand how to properly figure out that(code below) was an acceptable way to write it.
year % 4 == 0 and (year % 400 == 0 or year % 100 != 0)
i would like to understand or have some sort of guide on how to better interpret these questions.
iamphanisai yes. i too faced the same problem and had to google what a gregorian calendar was and found a page long explanation about how julias caesar invented it... etc etc before actually understanding what it means!
scotmatson Agree.
I am an English speaker and struggled with this definition. It was poorly written.
xbuildx_matrix I agree
kasunr My answers are ...
def is_leap(year): leap = False if year %4 == 0: if year %400 == 0: leap = True elif year %100 == 0: leap = False else: leap = True else: leap = False return leap
or
return (year %4 == 0 and year %100 != 0 or year %400 == 0)
JonathanV Working
if year%4 == 0 and (year%100 != 0 or year%400 == 0): leap = True
Vangelic_surgeon Thanks this stupid problem took me more time to solve and even the official solution is s**t
KavinRanawella if u are refering to the solution under the editorial tab, I would say, it is more elaborating. I think either you have misread the question, or you haven't noticed that there are no 'elseif' logic in the given solution. Only 'if' statements are there. It suits the requirements perfectly. Read the solution again carefully. U'll get it. :)
tricerabottoms This one is a little longer but I think you'll find it easier to follow:
class is_leap: pass is_leap.__init__ = lambda s,y: setattr(s,'y',y) is_leap.__repr__ = lambda s: str((not s.y%4)^(not s.y%100)^(not s.y%400))
hamichok11 lol :D much easier!
cssd1983 LOL
saumitra13325 LOL
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saumitra13325 [deleted]saumitra13325 Ahhh...got the end
bartyl :DDDD good joke
marinskiy Here is Python solution from my HackerrankPractice repository:
def is_leap(y): return y % 4 == 0 and (y % 100 != 0 or y % 400 == 0)
Feel free to ask if you have any questions :)
kiransajjanshet1 If the year is evenly divisible by 400, isnt it obviously divisible by 4 and 100 as well ? Can someone provide me an example where a year is divisible by 4, 400 but not 100 ? I am not sure if I am thinking right. Help please !
nitinchary The year that is evenly divisible by 4 and not divisible by 100 is a leap year. It has to satisfy both the conditions.
Ex: 2016-->This is evenly divisible by 4, but not divisible by 100. So 2016 is a leap year. 1800-->This is evenly divisible by 4 as well as 100. So 1800 is not a leap year.
Any year that is evenly divisible by 400 is a leap year. Ex: 2400--> This is divisible by 4 as well as 100, however, it is evenly divisible by 400. So that makes it a leap year.
divide_et_imper1 This code is working for Py2
def is_leap(year): leap = False if ((year % 4 == 0) and (year % 100 != 0)) or (year % 400 == 0): return True return leap
rishabh10 in the question it says evenly divisible doesn't that mean
(year/4)%2==0 ??
shifin_epz def is_leap(year): leap = False if year%4 == 0 and (year%100 != 0 or year%400 ==0): leap = True
return leap
cnhnyu If a year is a leap year: 1. it can be evenly divided by 4 and NOT evenly divided by 100; OR 2. it can be evenly divided by 400
leap = False if any([year % 4 == 0 and year % 4 != 0, year % 400 == 0]): leap = True
alexandar_naray1 I like the use of any here, I didn't think of that. You could set
leap = any([year % 4 == 0 and year % 4 != 0, year % 400 == 0])
since any returns a boolean
cnhnyu Thanks, you're right. It's much simpler.
leap = any([year % 4 == 0 and year % 100 != 0, year % 400 == 0])
Correction: year % 4 == 0 and year % 100 != 0
marcon_zm What is the comma doing here exactly?
year % 100 != 0, year % 400 == 0
Is it testing the output of "%100 != 0", and if it returns false it tests for the "% 400 == 0" conditional?
alexandar_naray1 the any function takes an iterable so it is basically saying: if any of the items in this iterable is true return true. so the comma makes them elements of a list between the brackets.
cnhnyu You can think it as an OR operation in this case.
alexandar_naray1 expains it very well.
mohamedfardinkh1 How to use "any" function? What are it's cases ?
bad_coder_lol for some reason, the Hacker Rank team wasn't able to clarify that clearly
agrawal_ved Using not: if not year % 4 and year % 100 or not year % 400 :
patrick_x99 that could evaluate to a number instead of True for years divisible by 4 but not 100. so you need to wrap it in a bool(...)
return bool(not year%4 and year%100 or not year%400)
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