[Python-ideas] Joining dicts again

[Markus Unterwaditzer]

On 2014-02-21 11:17, Cory Benfield wrote:
> On 21 February 2014 09:40,  <haael at interia.pl> wrote:
>> From what I read, it seems the biggest concern is: which value to pick 
>> up if both dicts have the same key.
>> a = {'x':1}
>> b = {'x':2}
>> c = a | b
>> print(c['x']) # 1 or 2?
>> 
>> My proposal is: the value should be derermined as the result of the 
>> operation 'or'. The 'or' operator returns the first operand that 
>> evaluates to boolean True, or the last operand if all are False.
>> 
>> So, provided we have 2 dicts 'a' and 'b' and c = a | b
>> 
>> 1. If a key is not present in 'a' nor 'b', then it is not present in 
>> c.
>> 2. If a key is present in 'a' and not in 'b', then c[k] = a[k].
>> 3. If a key is present in 'b' and not in 'a', then c[k] = b[k].
>> 4. If a key is present both in 'a' and 'b', then c[k] = a[k] or b[k].
> 
> This seems to me to be exactly the same as dict.update():
> 
> a = {'x': 1}
> b = {'x': 2}
> 
> c = b.copy()
> c.update(a)
> 

It seems that everybody misses the part of the OP where he states that 
conflict resolution shouldn't happen via "one dict wins" but rather with 
the "or"-operator.

> I'd be very reluctant to overload the bitwise-or operator to mean
> 'dictionary merging'. It's just not totally obvious to me that this is
> what would happen.
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