16.09.17 00:45, Terry Reedy пише:
On 9/15/2017 3:36 PM, Tim Chase wrote:
Looking through docs, I was unable to tease out whether there's a
prescribed behavior for the results of defining a dictionary with the
same keys multiple times
d = {
"a": 0,
"a": 1,
"a": 2,
}
In my limited testing, it appears to always take the last one,
resulting in
{"a": 2}
as if it iterated over the items, adding them to the dict, tromping
atop any previous matching keys in code-order.
Is this guaranteed by the language spec,
https://docs.python.org/3/reference/expressions.html#dictionary-displays
If a comma-separated sequence of key/datum pairs is given, they are
evaluated from left to right to define the entries of the dictionary:
each key object is used as a key into the dictionary to store the
corresponding datum. This means that you can specify the same key
multiple times in the key/datum list, and the final dictionary’s value
for that key will be the last one given.
Note that resulting dict can contain key/datum pairs not identical to
any key/datum pair in a sequence.
>>> {1: 2, True: 3}
{1: 3}
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