Appending object to a dictionary by key is replicating over the whole dictionary

Asked Dec 21 '16 at 12:45

Active Dec 21 '16 at 12:46

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I have been trying to create a dictionary consisting of pairs of keys and an array of tuples. Each "instrument" within the "subportfolio" would be one of such tuples, and my idea is to populate a dictionary based on one of the tuple fields containing the key for the dictionary. The code below shows my current implementation:

def assetClassBreakdown(subclasses, subportfolio):
    instrumentsDictionary = dict.fromkeys(subclasses, [])

    for instrument in subportfolio:
        # The subclass is in the ninth index within the instrument
        instrumentsDictionary[instrument[8]].append(instrument)

    return instrumentsDictionary

The problem is that every time I append a tuple based on the key (instrument[8]), it is appending this tuple to every key inside the dictionary. Basiclly, for every key I end up with exactly the same array of tuples.

edited Dec 21 '16 at 12:46

jonrsharpe

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asked Dec 21 '16 at 12:45

Diego St

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You'd be better off with `instrumentsDictionary = defaultdict(list)`. – jonrsharpe Dec 21 '16 at 12:47
@jonrsharpe if you could please point me to the original question I would be very grateful. – Diego St Dec 21 '16 at 12:47
There is literally a link in the header of this page. – jonrsharpe Dec 21 '16 at 12:48
@jonrsharpe thank you beautiful man – Diego St Dec 21 '16 at 12:50

Appending object to a dictionary by key is replicating over the whole dictionary

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