How to create a dictionary from a list of tuples without overwriting the first unique key value?

Question

So I've got a list of tuples with a key and its corresponding value. I wanted to have it be displayed as a dictionary, so I wrote

def tup_to_dict (lst):
    return dict(lst)

Now if my lst was [("A3", "green"), ("B5", "blue"), ("A3", "yellow")] , my output would then be:

{'B5': 'blue', 'A3': 'yellow'}

How would I go about checking if a key was already assigned a value and not overwriting it if it was. So that my output would look like this:

{"A3": "green", "B5": "blue"}

Thanks!

Answer 1

dict使用最后一个值，您想使用第一个值…交换它们！

return dict(reversed(lst))

Answer 2

This also works:

a = [("A3", "green"), ("B5", "blue"), ("A3", "yellow")]
b = dict((x,y) for x,y in reversed(a))