Adding multiple keys of the same name to a dict should raise an exception but instead causes a different behavior. For example consider this code,

>>> d = {"x" : "First value", "x" : "Second value", "y" : "Third value"}

One would expect a error because there two keys with the same name or that Python will add "x" : "First value" and will skip "x" : "Second value". But the result is opposite,

>>> d
{'x': 'Second value', 'y': 'Third value'}

Is this a bug or is this an intended behavior? (I may have missed out information related to this in the documentation. Kindly correct me if that's the case.)

Looks like a duplicate of https://bugs.python.org/issue16385

I've read that issue but it seems that it actually was based on "Should there be a warning or error?". I actually suggest something different. I suggest that "Either raise an exception or just use the first key-value pair if the key is repeated during initialization". (By "initialization" I mean to say creating a new dict object)

Looks like the same issue to me as the rejected issue that Karthikeyan mentioned. Changing it to use the first value is a non-starter because it would break compatibility. I'd suggest using a linter that warns about duplicate keys in literals; we implemented that internally.

Ok. I'm closing this then. (I wasn't aware that this was an intended behavior.)