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Is there a way to automatically convert an object into a string before its used as a key in a dictionary – python

April 25, 2022

I have a partially weird question. Basically i was wondering if there is an easy way to essentially have multiple keys in a dictionary for one value. An example of what i would like to achieve is as following:

class test:
    key="test_key"
    
    def __str__(self):
        return self.key

tester = test()

dictionary = {}
dictionary[tester] = 1

print(dictionary[tester])
print(dictionary["test_key"])

where the output would be:

>>> 1
>>> 1

What I’m looking for is essentially to auto convert the object to a string before its used as a key. Is this possible?

Thanks so much.

>Solution :

Personally, I think it’s better to explicitly cast the object to a string, e.g.

dictionary[str(tester)] = 1

That being said, if you’re really really REALLY sure you want to do this, define the __hash__ and __eq__ dunder methods. No need to create a new data structure or change the existing code outside of the class definition:

class test:
    key="test_key"
    
    def __hash__(self):
        return hash(self.key)
        
    def __eq__(self, other):
        if isinstance(other, str):
            return self.key == other
        return self.key == other.key
    
    def __str__(self):
        return self.key

This will output: