Python – Convert list to Single Dictionary Key Value list

Last Updated : 03 Jul, 2020

Sometimes, while working with Python lists, we can have a problem in which we need to convert the list into a dictionary, which has single key, the Kth element of list, and others as it’s list value. This kind of problem can have application in data domains. Let’s discuss certain ways in which this task can be performed.

Input : test_list = [6, 5, 3, 2], K = 1
Output : {5 : [6, 3, 2]}
Input : test_list = [6, 5, 3, 2], K = 2
Output : {5 : [6, 5, 2]}

Method #1 : Using loop
This is one of the ways in which this task can be performed. In this, we create a key initially and then append values except K index to create dictionary list.

# Python3 code to demonstrate working of 
# Convert list to Single Dictionary Key Value list
# Using loop
  
# initializing list
test_list = [5, 6, 3, 8, 9] 
  
# printing original list
print("The original list is : " + str(test_list))
  
# initializing K 
K = 3
  
# Convert list to Single Dictionary Key Value list
# Using loop
res = {test_list[K] : []}
for idx in range(len(test_list)):
    if idx != K:
        res[test_list[K]].append(test_list[idx])
  
# printing result 
print("Records after conversion : " + str(res))

Output :

The original list is : [5, 6, 3, 8, 9]
Records after conversion : {8: [5, 6, 3, 9]}

Method #2 : Using list slicing
This is yet another one liner in which this task can be performed. In this, we slice out the list on Kth index and assign as values in dictionary.

# Python3 code to demonstrate working of 
# Convert list to Single Dictionary Key Value list
# Using loop
  
# initializing list
test_list = [5, 6, 3, 8, 9] 
  
# printing original list
print("The original list is : " + str(test_list))
  
# initializing K 
K = 3
  
# Convert list to Single Dictionary Key Value list
# Using loop
res = {test_list[K] : test_list[:K] + test_list[K + 1:]}
  
# printing result 
print("Records after conversion : " + str(res))

Output :

The original list is : [5, 6, 3, 8, 9]
Records after conversion : {8: [5, 6, 3, 9]}

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Python – Convert list to Single Dictionary Key Value list