tuples to dictionary with two occurances-CodePudding

My question is how to turn two tuples in a dictionary, and have it so that if there are two strings that are the same in the first tuple, it returns the first element from the second tuple:

e.g.

def tuples_to_dict(x,y):
    mydict= {}
    
    for k,v in zip(x,y):
        mydict[k]=v
    return mydict

tuples_to_dict(('a','b', 'c', 'a'), (1,2,3,4))

however this outputs:

{'a': 4, 'b': 2, 'c': 3}

However I would like it to be:

{'a': 1, 'b': 2, 'c': 3}

Apologies if this is too simple a question to be stuck on! I know I have to add more to my code which is why its returning the wrong output I want, I've had a look at other resources however it doesnt answer my specific question. I've thought about putting an if statement and do x.count(k)>=1: However I didnt know where to go from there.

CodePudding user response：

Just one extra check needed to see whether the key is already in the dictionary.

def tuples_to_dict(x,y):
    mydict= {}
    
    for k,v in zip(x,y):
        if k not in mydict:
            mydict[k]=v
    return mydict

CodePudding user response：

Inserting the element in reversed order would achieve what you need:

def tuples_to_dict(x, y):
    return dict(reversed(list(zip(x, y))))

tuples_to_dict(('a', 'b', 'c', 'a'), (1, 2, 3, 4))

OUTPUT

{'a': 1, 'c': 3, 'b': 2}

Ideally you should check that the two lists have the same length, to avoid unexpected results: zip will truncate to the shortest list by default.

There could be a debate if reversing before or after zipping, but I think the latter is better for the following reason - if you pass list of different lengths:

x = ('a', 'b', 'c', 'a') 
y = (1, 2, 3)

dict(reversed(list(zip(x, y))))

dict(zip(reversed(x), reversed(y)))

OUTPUT

{'c': 3, 'b': 2, 'a': 1}  # This is more in line with what I would expect
{'a': 3, 'c': 2, 'b': 1}

In Python 3.10 you can force zip to throw an exception in case the zipped lists have different lengths (passing strict=True), and that would avoid any issue in this respect.