CODEWITHSUNDEEP
pythonarrays
user2348621
user2348621

Reputation: 27

How do you find odd elements in an array?

def fillaray(size):

    num = [0] * size
    num = [random.randint(0,9) for i in range(size)]
    print(num)

    return num


def totalOdds(num, size):

    for i in range (size):
        if i % 2 ==0:
            odd = num[i]
            i+1
    print(odd)

As you can see in def totalOdds()I'm trying to separate the odd elements from the array "num." I plan on adding all the values in the odd elements up. Can someone point me in the right direction to what I'm doing wrong?

Thanks.

Upvotes: 1

Views: 10106

Answers (4)

marcadian
marcadian

Reputation: 2618

  1. You are not summing them
  2. i+1 is doing nothing

to get all odd elements

odds = [n for n in nums if n%2]

to get only the sum of odd elements

sum_odds = sum(n for n in sums if n % 2)

Upvotes: 3

HennyH
HennyH

Reputation: 7944

nums = [1,2,3,4,5,6,7,8,9,10,11,12]
odds = [ n for n in nums if n%2 ]
print odds

Gives:

>>> 
[1, 3, 5, 7, 9, 11]

This can be put into a function like so:

def getOdds(aList):
    return [ n for n in aList if n%2 ]

Example usage:

myOdds = getOdds(nums)
print("{0} has {1} odd numbers which were {2}".format(nums,len(myOdds),myOdds))
print("The odd numbers sum to {0}".format(sum(myOdds)))

Produces:

>>> 
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12] has 6 odd numbers which were [1, 3, 5, 7, 9, 11]
The odd numbers sum to 36

As to what you're doing wrong, you're iterating over an iterable containing the elements 0 to size this won't always be the value of num (unless num is indeed range(size)). Once you make i represent a value in num which you're iterating over, if i%2 == 0 will mean it's even, if you want odds, the number musn't be divisible by two. Hence this should be changed to either if i%2 != 0 or if i%2. You will also have to declare the odd list before the for i ... loop, so you can append the numbers in num which meet the condition in the if i%2 selection control structure. You should appened the number in num by doing odd.append(i), at the moment you're reassigning odd a new value. You also should not be incrementing i. 'i' should represent a number in num not the index of the number in num.

Upvotes: 1

mpen
mpen

Reputation: 283133

Can be done in one line:

print sum(x for x in num if x & 1)

Also, see my comment under the question for where you went wrong.

Upvotes: 1

asheeshr
asheeshr

Reputation: 4114

If you are trying to find the sum of elements at odd places in the array :

def totalOdds(num, size):

    for i in range(size):
        if i % 2 ==0 :
            odd += num[i]
    print(odd)

If you are trying to sum the odd valued elements :

def totalOdds(num, size):

    for i in range(size):
        if num[i] % 2 !=0 :
            odd += num[i]
    print(odd)

Upvotes: 0

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