Replace the keys of one dictionary with the values from another IF the keys of both dictionaries mat-CodePudding

I have two dictionaries.

a = {3: 1, 14: 2, 4: 3, 1: 4, 5: 5, 16: 6, 2: 7, 6: 8, 15: 9, 10: 10, 7: 11, 9: 12, 8: 13, 12: 14, 13: 15, 11: 16} 
b = {1: 29, 2: 63, 3: 29, 4: 32, 5: 46, 6: 29, 7: 24, 8: 63, 9: 67, 10: 46, 11: 29, 12: 24, 13: 67, 14: 2, 15: 63, 16: 2, 17: 42}

I want to assign the values of a to the values of b if the keys match. Or some other similar result. I've been learning Python for about a week and I'm pretty sure the answer involves list comprehension but I just can't get my ahead around some of the other answers on here so a step by step for loop style answer would be much appreciated. Thanks

CodePudding user response：

Iterate over the set of keys in a and if that key exists in b, set b's value at that key to the value of a at that key

for key in a.keys():
    if key in b:
      b[key] = a[key]

Hope it helped

CodePudding user response：

You can loop the dict a.

Add a condition if a key exist in dict b

If they match, assign the dict b with key as the value from the dict a

for _a in a:
    if _a in b:
        b[_a] = a[_a]

CodePudding user response：

a = {3: 1, 14: 2, 4: 3, 1: 4, 5: 5, 16: 6, 2: 7, 6: 8, 15: 9, 10: 10, 7: 11, 9: 12, 8: 13, 12: 14, 13: 15, 11: 16} 
b = {1: 29, 2: 63, 3: 29, 4: 32, 5: 46, 6: 29, 7: 24, 8: 63, 9: 67, 10: 46, 11: 29, 12: 24, 13: 67, 14: 2, 15: 63, 16: 2, 17: 42}

a_list = list(a)
b_list = list(b)
for key in range(len(a_list)):
    if b_list[key] == a_list[key]:
        b[b_list[key]] = a[a_list[key]]


print(b)

outputs {1: 29, 2: 63, 3: 29, 4: 32, 5: 5, 6: 29, 7: 24, 8: 63, 9: 67, 10: 10, 11: 29, 12: 24, 13: 67, 14: 2, 15: 63, 16: 2, 17: 42}

not sure if this is the output you wanted

CodePudding user response：

In your example, the keys of a are a subset of the keys of b. If that's not just a bad example but always the case, you can just do b.update(a).

CodePudding user response：

a = {3: 1, 14: 2, 4: 3, 1: 4, 5: 5, 16: 6, 2: 7, 6: 8, 15: 9, 10: 10, 7: 11, 9: 12, 8: 13, 12: 14, 13: 15, 11: 16} 
b = {1: 29, 2: 63, 3: 29, 4: 32, 5: 46, 6: 29, 7: 24, 8: 63, 9: 67, 10: 46, 11: 29, 12: 24, 13: 67, 14: 2, 15: 63, 16: 2, 17: 42}

for key_a, value_a in a.items():
    for key_b, value_b in b.items():
        if(key_a == key_b):
            b[key_b] = value_a
print(b)

Output:

{1: 4, 2: 7, 3: 1, 4: 3, 5: 5, 6: 8, 7: 11, 8: 13, 9: 12, 10: 10, 11: 16, 12: 14, 13: 15, 14: 2, 15: 9, 16: 6, 17: 42}