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Python program to count Even and Odd numbers in a List

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Given a list of numbers, write a Python program to count Even and Odd numbers in a List.

Example:

Input: list1 = [2, 7, 5, 64, 14]
Output: Even = 3, odd = 2

Input: list2 = [12, 14, 95, 3]
Output: Even = 2, odd = 2

Example 1: 

Count Even and Odd numbers from the given list using for loop Iterate each element in the list using for loop and check if num % 2 == 0, the condition to check even numbers. If the condition satisfies, then increase the even count else increase odd count. 

Python3




# Python program to count Even
# and Odd numbers in a List
 
# list of numbers
list1 = [10, 21, 4, 45, 66, 93, 1]
 
even_count, odd_count = 0, 0
 
# iterating each number in list
for num in list1:
 
    # checking condition
    if num % 2 == 0:
        even_count += 1
 
    else:
        odd_count += 1
 
print("Even numbers in the list: ", even_count)
print("Odd numbers in the list: ", odd_count)


Output:

Even numbers in the list:  3
Odd numbers in the list:  4

Time Complexity: O(N), Here N is the number of elements in the list.
Auxiliary Space: O(1), As constant extra space is used.

Example 2: Using while loop 

Python3




# Python program to count Even and Odd numbers in a List
 
# list of numbers
list1 = [10, 21, 4, 45, 66, 93, 11]
 
even_count, odd_count = 0, 0
num = 0
 
# using while loop    
while(num < len(list1)):
     
    # checking condition
    if list1[num] % 2 == 0:
        even_count += 1
    else:
        odd_count += 1
     
    # increment num
    num += 1
     
print("Even numbers in the list: ", even_count)
print("Odd numbers in the list: ", odd_count)


Output:

Even numbers in the list:  3
Odd numbers in the list:  4

Time Complexity: O(N), Here N is the number of elements in the list.
Auxiliary Space: O(1), As constant extra space is used.

Example 3: Using Python Lambda Expressions 

Python3




# list of numbers
list1 = [10, 21, 4, 45, 66, 93, 11]
 
odd_count = len(list(filter(lambda x: (x%2 != 0) , list1)))
 
# we can also do len(list1) - odd_count
even_count = len(list(filter(lambda x: (x%2 == 0) , list1)))
 
print("Even numbers in the list: ", even_count)
print("Odd numbers in the list: ", odd_count)


Output:

Even numbers in the list:  3
Odd numbers in the list:  4

Time Complexity: O(n)
Space Complexity: O(1)

Example 4: Using List Comprehension 

Python3




# Python program to print odd Numbers in a List
 
# list of numbers
list1 = [10, 21, 4, 45, 66, 93, 11]
 
only_odd = [num for num in list1 if num % 2 == 1]
odd_count = len(only_odd)
 
print("Even numbers in the list: ", len(list1) - odd_count)
print("Odd numbers in the list: ", odd_count)


Output:

Even numbers in the list:  3
Odd numbers in the list:  4

Time Complexity: O(N), Here N is the number of elements in the list.
Auxiliary Space: O(1), As constant extra space is used.

Example 5: Using Recursion

Python3




# Python program to count Even
# and Odd numbers in a List
# using recursion
even_count = 0  # even counter
i = 0  # index, so that we can check if list[i] is even or odd
odd_count = 0  # odd counter
 
 
def evenoddcount(lst):
    # defining local counters as global variable
    global even_count
    global odd_count
    global i
    if lst[i] % 2 == 0# check if number is even
        even_count += 1
    else# if number is odd
        odd_count += 1
    if i in range(len(lst)-1):
        i += 1  # increment i
        evenoddcount(lst)  # calling fonction recursively
    else:
        print("Even numbers in the list: ", even_count)
        print("Odd numbers in the list: ", odd_count)
 
 
list1 = [10, 21, 4, 45, 66, 93, 1]
evenoddcount(list1)


Output

Even numbers in the list:  3
Odd numbers in the list:  4

Time Complexity: O(N), Here N is the number of elements in the list.
Auxiliary Space: O(1), As constant extra space is used.

Example 6: Using Bitwise XOR operator

The idea is to check whether the last bit of the number is set or not. If the last bit is set then the number is odd, otherwise even. As we know bitwise XOR Operation of the Number by 1 increments the value of the number by 1 if the number is even otherwise it decrements the value of the number by 1 if the value is odd.

CHECK IF NUMBER IS EVEN OR ODD USING XOR OPERATOR


Python3




# Python program to count Even
# and Odd numbers in a List
# using Bitwise XOR
 
# list of numbers
list1 = [10, 21, 4, 45, 66, 93, 1]
 
even_count, odd_count = 0, 0
for num in list1:
 
    # checking condition
    if num ^ 1 == num + 1:
        even_count += 1
 
    else:
        odd_count += 1
 
print("Even numbers in the list: ", even_count)
print("Odd numbers in the list: ", odd_count)
# This code is contributed by Shivesh Kumar Dwivedi


Output

Even numbers in the list:  3
Odd numbers in the list:  4

Time Complexity: O(N), Here N is the number of elements in the list.
Auxiliary Space: O(1), As constant extra space is used.

Example 7: Using Bitwise AND operator

The idea is to check whether the last bit of the number is set or not. If the last bit is set then the number is odd, otherwise even.
As we know bitwise AND Operation of the Number by 1 will be 1, If it is odd because the last bit will be already set. Otherwise, it will give 0 as output. 

Python3




# Python program to count Even
# and Odd numbers in a List
# using Bitwise AND
 
# list of numbers
list1 = [10, 21, 4, 45, 66, 93, 1]
 
even_count, odd_count = 0, 0
for num in list1:
 
    # checking condition
    if not num & 1:
        even_count += 1
 
    else:
        odd_count += 1
 
print("Even numbers in the list: ", even_count)
print("Odd numbers in the list: ", odd_count)


Output

Even numbers in the list:  3
Odd numbers in the list:  4

Time Complexity: O(N), Here N is the number of elements in the list.
Auxiliary Space: O(1), As constant extra space is used.

Example 8: Using Bitwise OR operator

The idea is to check whether the last bit of the number is set or not. If the last bit is set then the number is odd, otherwise even. As we know bitwise OR Operation of the Number by 1 increment the value of the number by 1 if the number is even otherwise it will remain unchanged. So, if after OR operation of number with 1 gives a result which is greater than the number then it is even and we will return true otherwise it is odd and we will return false.

Python3




# Python program to count Even
# and Odd numbers in a List
# using Bitwise OR
 
# list of numbers
list1 = [10, 21, 4, 45, 66, 93, 1]
 
even_count, odd_count = 0, 0
for num in list1:
       
    # checking condition
    if num | 1 > num:
        even_count += 1
   
    else:
        odd_count += 1
           
print("Even numbers in the list: ", even_count)
print("Odd numbers in the list: ", odd_count)
# This code is contributed by Shivesh Kumar Dwivedi


Output

Even numbers in the list:  3
Odd numbers in the list:  4

Time Complexity: O(N), Here N is the number of elements in the list.
Auxiliary Space: O(1), As constant extra space is used.

Method: Using the enumerate function 

Python3




lst = [12, 14, 95, 3];c=0;c1=0
for i,a in enumerate(lst):
    if a%2==0:
        c+=1
    else:
        c1+=1
     
print("even number count",c,"odd number count",c1)


Output

even number count 2 odd number count 2

Time Complexity: O(N), Here N is the number of elements in the list.
Auxiliary Space: O(1), As constant extra space is used.

Method: Using Numpy.Array : 

Python




# Python program to Print Positive Numbers in a List
import numpy as np
 
# list of numbers
List = [10, 21, 4, 45, 66, 93, 11]
 
# using numpy Array
list1 = np.array(List)
Even_list = list1[list1 % 2 == 0]
 
print("Even numbers in the list: ", len(Even_list))
print("Odd numbers in the list: ", len(list1)-len(Even_list))


Output:

Even numbers in the list:  3
Odd numbers in the list:  4

Time Complexity: O(N), Here N is the number of elements in the list.
Auxiliary Space: O(1), As constant extra space is used.

Method: Using Numpy.where() function : 

note: install numpy module using command “pip install numpy”

Algorithm:

Convert the given list to a numpy array.
Use numpy.where() function to find the indices of even and odd numbers in the array.
Count the number of indices using the len() function.
Print the counts.

Here’s the Python program to count Even and Odd numbers in a List using numpy.where() function:

Python3




import numpy as np
 
# list of numbers
list1 = [2, 7, 5, 64, 14]
 
# create numpy array from list
arr = np.array(list1)
 
# count even numbers
even_count = len(np.where(arr % 2 == 0)[0])
 
# count odd numbers
odd_count = len(np.where(arr % 2 == 1)[0])
 
# print counts
print("Even numbers in the list: ", even_count)
print("Odd numbers in the list: ", odd_count)


Output:

Even numbers in the list:  3
Odd numbers in the list:  2

Time Complexity: O(N), where N is the number of elements in the list.
Space Complexity: O(N), as we create a numpy array of size N.

Method: Using Sum and len function  

Approach: 

  • Initialize list. 
  • Initialize even_count and odd_count variables to store numbers. 
  • Use Sum method which counts 1 if the number in the list is odd and store the result in odd_count. 
  • Subtract the total length list to odd_count and store the value in even_count. 
  • Print event_count and odd_count. 

Python3




# Python program to count Even
# and Odd numbers in a List
 
# list of numbers
list1 = [10, 21, 4, 45, 66, 93, 1]
 
even_count, odd_count = 0, 0
 
# Using sum function
odd_count = sum(1 for i in list1 if i&1)
even_count = len(list1) - odd_count
 
print("Even numbers in the list: ", even_count)
print("Odd numbers in the list: ", odd_count)


Output:

Even numbers in the list:  3
Odd numbers in the list:  4

Time Complexity: O(n), where n is the length of the list.
Space Complexity: O(1), Because no extra space is used.



Last Updated : 22 Apr, 2023
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