Python – Odd elements indices

Sometimes, while working with Python lists, we can have a problem in which we wish to find Odd elements. This task can occur in many domains such as web development and while working with Databases. We might sometimes, require to just find the indices of them. Let’s discuss certain way to find indices of Odd elements.

Method #1 : Using loop
This is brute force method in which this task can be performed. In this, we check for odd element in list and append its index accordingly.

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# Python3 code to demonstrate working of 
# Odd elements indices
# using loop 
  
# initialize list 
test_list = [5, 6, 10, 4, 7, 1, 19
  
# printing original list 
print("The original list is : " + str(test_list)) 
  
# Odd elements indices
# using loop 
res = [] 
for idx, ele in enumerate(test_list): 
    if ele % 2 != 0
        res.append(idx) 
          
# printing result 
print("Indices list Odd elements is : " + str(res)) 

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Output :

The original list is : [5, 6, 10, 4, 7, 1, 19]
Indices list Odd elements is : [0, 4, 5, 6]

 

Method #2 : Using list comprehension
This is the shorthand by which this task can be performed. This method works in similar way as the above method. The difference is that it’s a one liner.



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# Python3 code to demonstrate working of 
# Odd elements indices
# using list comprehension 
  
# initialize list 
test_list = [5, 6, 10, 4, 7, 1, 19
  
# printing original list 
print("The original list is : " + str(test_list)) 
  
# Odd elements indices
# using list comprehension 
res = [idx for idx, ele in enumerate(test_list) if ele % 2 != 0
          
# printing result 
print("Indices list Odd elements is : " + str(res)) 

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Output :

The original list is : [5, 6, 10, 4, 7, 1, 19]
Indices list Odd elements is : [0, 4, 5, 6]

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