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# Python | Union of lists of values

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Method # 1: Using Loops
Using loops is a naive crude method for this particular task. In this method, we check for the presence of keys in both lists and check for non-duplicate values ​​to add to the result. We even check for keys not found in others to add the value of the entire list.

 ` # Python3 demo code ` ` # Union of lists of values ​​` ` # using loops `   ` # dict initialization ` ` test_dict1 ` ` = ` ` {` ` "Key1" ` `: [` ` 1 ` `, ` ` 3 ` `, ` ` 4 ` `], ` ` "key2" ` `: [` ` 4 ` `, ` ` 5 ` `]} `` test_dict2 = { "Key1" : [ 1 , 7 , 8 ]}   # printing original dictations print ( "The original dict 1:" + str (test_dict1)) print ( "The original dict 2:" + str (test_dict2))   # use Using loops # Union of lists of values ​​ for key in test_dict1:  if key in test_dict2:    for val in test_dict1 [key]:   if val not in test_dict2 [key]:    test_dict2 [key] .append (val)   else :    test_dict2 [key] = test_dict1 [key] [:]    # print result print ( "The dicts after union is:" + str (test_dict2)) `

Output:

` The original dict 1: {’Key1’: [1, 3, 4],’ key2’: [4, 5]} The original dict 2: {’Key1’: [1, 7, 8]} The dicts after union is: {’Key1’: [1, 7, 8, 3, 4],’ key2’: [4, 5]} `

Method # 2: Using dictionary comprehension + typing operation
This is a one-line approach to solve a similar problem, offering a compact alternative to the above method. This solution is handled using the given comprehension to combine the required elements into lists using dictionary comprehension.

 ` # Python3 demo code ` ` # Union of lists of values ​​` ` # using dictionary comprehension + set operations `   ` # dict initialization ` ` test_dict1 ` ` = ` ` {` ` "Key1" ` `: [ ` ` 1 ` `, ` ` 3 ` `, ` ` 4 ` `], ` ` "key2" ` `: [` ` 4 ` `, ` ` 5 ` `]} ` ` test_dict2 ` ` = ` ` {` ` "Key1" ` `: [` ` 1 ` `, ` ` 7 ` `, ` ` 8 ` `] } `   ` # printing original dictations ` ` print ` ` (` ` "The original dict 1:" ` ` + ` ` str ` ` (test_dict1)) ` ` print ` ` (` ` "The original dict 2:" ` ` + ` ` str ` ` (test_dict2)) `   ` # using dictionary comprehension + operations on sets ` ` # Union of lists of values ​​` ` res ` ` = ` ` {key: ` ` list ` ` (` ` set ` ` (test_dict1.get (key, []) ` ` + ` ` test_dict2.get (key, []))) ` ` ` ` for ` ` key ` ` in ` ` set ` ` (test_dict2) | ` ` set ` ` (test_dict1)} `   ` # print result ` ` print ` ` (` ` "The dicts after union is:" ` ` + ` ` str ` ` (res)) `

Exit:

` The original dict 1: {’Key1’: [1, 3, 4],’ key2’: [4, 5]} The original dict 2: {’Key1’: [1 , 7, 8]} The dicts after union is: {’Key1’: [1, 7, 8, 3, 4],’ key2’: [4, 5]} `

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