Python | Combine two lists by maintaining duplicates in first list

Given two lists, the task is to combine two lists and removing duplicates, without removing duplicates in original list.

Example:

Input : 
list_1 = [11, 22, 22, 15]
list_2 = [22, 15, 77, 9]

Output :
OutList = [11, 22, 22, 15, 77, 9]

Code #1: using extend

# Python code to combine two lists 
# and removing duplicates, without 
# removing duplicates in original list. 
  
# Initialisation of first list 
list1 = [111, 222, 222, 115] 
  
# Initialisation of Second list 
list2 = [222, 115, 77, 19] 
  
output = list(list1) 
  
# Using extend function 
output.extend(y for y in list2 if y not in output) 
  
# printing result 
print(output) 

Output:

[111, 222, 222, 115, 77, 19]

Code #2 : Using Set and Iteration
Append those element in first list which are not in second list and then take union of first and second list.

# Python code to combine two lists  
# and removing duplicates, without  
# removing duplicates in original list. 
  
# Initialisation of first list 
list1 = [11, 22, 22, 15] 
  
# Initialisation of Second list 
list2 = [22, 15, 77, 9] 
  
# creating set 
unique_list1 = set(list1) 
unique_list2 = set(list2) 
  
# Difference in two sets 
diff_element = unique_list2 - unique_list1 
  
# union of difference + first list 
output = list1 + list(diff_element) 
  
# printing output 
print(output)  

Output:

[11, 22, 22, 15, 9, 77]

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