How this code works, can anybody help me to understand this code.

Question

The code is-
def is_even(x):
if x == 0:
return True
else:
return is_odd(x-1)

def is_odd(x):
return not is_even(x)

print(is_odd(2))
print(is_even(1))
print (is_odd(1))
print (is_even(2))

Output:-
False
False
True
True

https://code.sololearn.com/cvOzs768zjjt/?ref=app

Help me to understand the working of that code/program.

Answer 1

ミ Shiva 彡

These functions are working by calling themself one by one. And lastly it ends on is_even() function with a zero value.

if we pass 2 to a is_even() function,

is_even(2)=>return is_odd(1)=>return not is_even(1)=>return is_odd(0)=>return not is_even(0)=>return True

So,
is_even(2)=>(return not(return not(return True)))
return(not(not(True)))
return (not(False))=True

if we pass 3 to a is_odd() function,

is_odd(3)=>return not is_even(3)=>return is_odd(2)=>return not is_even(2)=>return is_odd (1)=>return not is_even(1)=>return is_odd(0)=>return not is_even(0)=>return True

So,
is_odd(3) =>return(not(not(not(not(True))))) =return(True)=True

Answer 2

Try thinking through what happens with a call to each of the functions with the smallest even (2) and odd (1) numbers and then apply that to any other even or odd call to those functions as they will have the same results.
is_even(1)
is_odd(1)
is_even(2)
is_even(2)

Answer 3

ミ Shiva 彡 ,

you don't need 2 functions to check for even or odd. use one function, pass a number as argument to it, and the function will return True or False :

def is_even(x):
if x%2 == 0:
return True
else:
return False

print(is_even(2))
print(is_even(1))

if you like it the short way, you can replace the whole function like this:

def is_even(x):
return True if x%2==0 else False

Answer 4

˜”*°•.˜”*°• Mohan 333 •°*”˜.•°*”˜ Ok and
Thanks for giving your precious time

Answer 5

ミ Shiva 彡 I know: I was only replying to Lothar ;P

Answer 6

ChaoticDawg Can you explain it in brief

Answer 7

ミ Shiva 彡
Yeah, I forget to type that. Now, I corrected see that 👆.

Answer 8

# Lothar the shortest way (wich return True or False) and most efficient way would be:

is_even = lambda x: x&1==0

# and returning 1 or 0 is even shortest:

is_even = lambda x: x&1^1
is_odd = lambda x: x&1

Answer 9

Lothar
Thanks for suggesting
But i don't want a simpler or easy way of knowing even or odd number,
I want to know how the program works.
Again thanks 😊
I agree with you

Answer 10

visph Thanks you for giving me a simpler way
I agree with you
But i want to know the working of program not any simple way.

Again, thanks 😊

Answer 11

The number in perinthesis in
print(is_odd(1)) translates to x in the is_odd(x): function
And when print(is_odd(2)) runs, it will first read the is_odd(x) function and when it calls is_even(x) in the line:
“return not is_even(x)”, it will also return the opposite bool, so when x, or 1 in this case, is subtracted by one in the line
return is_odd(x-1)
It will go back to the is_odd(x) function and that will make it go back, but now, if is_even(x) is true, it will return true since the odd function said not twice, a double negative, which results in a positive so when it says x = 0, and it returns true, it will print true. If the print() said instead
print(is_even(1))
It would start with is_even(x) and x would become 0, and when it comes back from the is_odd function, it will return the opposite boolean (true/false) and we would get a false as our output, hope this helped!

Answer 12

Ajay Parimi Please don't spam.

Answer 13

Carolina Humphrey Please keep your comments 13+. Your comment has been reported. It's not acceptable to post any NSFW content in a coding platform. SoloLearn is not Tinder.

Answer 14

˜”*°•.˜”*°• Mohan 333 •°*”˜.•°*”˜ As you say-
is_even(2) gives a output of False

But it's not correct it will give output of True

Answer 15

ミ Shiva 彡 Here are the one-liner lambda functions:

is_even, is_odd = lambda x: not x & 1, lambda x: x & 1

print(is_even(78))
print(is_odd(78))

# Hope this helps

Answer 16

Odd

Answer 17

U no some off coding to learn easy

Answer 18

Hello

Answer 19

Hi

Answer 20

I want to learn coding easy in mobile