Python – Cross mapping of Two dictionary value lists

21 Jun, 2022
GIven two dictionaries with list values, perform mapping of keys of first list with values of other list, by checking values-key linkage.
Input : test_dict1 = {“Gfg” : [4, 10], “Best” : [8, 6], “is” : [9, 3]}, test_dict2 = {6 : [15, 9], 8 : [6, 3], 7 : [9, 8], 9 : [10, 11]} Output : {‘Best’: [6, 3, 15, 9], ‘is’: [10, 11]} Explanation : “Best” has 8 and 6, which are mapped to 6, 3 and 15, 9 hence output for that key. Input : test_dict1 = {“Gfg” : [4, 10], “Best” : [18, 16], “is” : [9, 3]}, test_dict2 = {6 : [15, 9], 8 : [6, 3], 7 : [9, 8], 9 : [10, 11]} Output : {‘is’: [10, 11]} Explanation : Only 9 present as possible key.
Method #1 : Using loop + setdefault() + extend()
The combination of above functions can be used to solve this problem. In this, we perform the task of getting the matching keys with values using get() and setdefault is used to construct empty list for mapping.
Python3
# Python3 code to demonstrate working of# Cross mapping of Two dictionary value lists# Using loop + setdefault() + extend() # initializing dictionariestest_dict1 = {"Gfg" : [4, 7], "Best" : [8, 6], "is" : [9, 3]}test_dict2 = {6 : [15, 9], 8 : [6, 3], 7 : [9, 8], 9 : [10, 11]} # printing original listsprint("The original dictionary 1 is : " + str(test_dict1))print("The original dictionary 2 is : " + str(test_dict2)) res = {} # getting all values of first dictionaryfor key, val in test_dict1.items():    for key1 in val:                 # getting result with default value list and extending        # according to value obtained from get()        res.setdefault(key, []).extend(test_dict2.get(key1, [])) # printing resultprint("The constructed dictionary : " + str(res))
The original dictionary 1 is : {'Gfg': [4, 7], 'Best': [8, 6], 'is': [9, 3]}
The original dictionary 2 is : {6: [15, 9], 8: [6, 3], 7: [9, 8], 9: [10, 11]}
The constructed dictionary : {'Gfg': [9, 8], 'Best': [6, 3, 15, 9], 'is': [10, 11]}
Method #2 : Using list comprehension + dictionary comprehension
This is one more way in which this problem can be solved. In this, we extract all the mapping using list comprehension and then construct new dictionary by cross-mapping the extracted values.
Python3
# Python3 code to demonstrate working of# Cross mapping of Two dictionary value lists# Using list comprehension + dictionary comprehension # initializing dictionariestest_dict1 = {"Gfg" : [4, 7], "Best" : [8, 6], "is" : [9, 3]}test_dict2 = {6 : [15, 9], 8 : [6, 3], 7 : [9, 8], 9 : [10, 11]} # printing original listsprint("The original dictionary 1 is : " + str(test_dict1))print("The original dictionary 2 is : " + str(test_dict2)) # using internal and external comprehension to# solve problemres = {key: [j for i in val if i in test_dict2 for j in test_dict2[i]]      for key, val in test_dict1.items()} # printing resultprint("The constructed dictionary : " + str(res))
The original dictionary 1 is : {'Gfg': [4, 7], 'Best': [8, 6], 'is': [9, 3]}
The original dictionary 2 is : {6: [15, 9], 8: [6, 3], 7: [9, 8], 9: [10, 11]}
The constructed dictionary : {'Gfg': [9, 8], 'Best': [6, 3, 15, 9], 'is': [10, 11]}
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