I have a list of dictionaries
input:
x = [{'id': 19, 'number': 123, 'count': 1},
{'id': 1, 'number': 23, 'count': 7},
{'id': 2, 'number': 238, 'count': 17},
{'id': 1, 'number': 9, 'count': 1}]
How would I get the list of number:
[123, 23, 238, 9]
Thank you for you reading
To get these numbers you can use
>>> [ d['number'] for d in x ]
But this is not the "list of keys" for which you ask in the question title.
The list of keys of each dictionary d in x is obtained as d.keys()
which would yield something like ['id', 'number', ...]. Do for example
>>> [ list(d.keys()) for d in x ]
to see. If they are all equal you are probably only interested in the first of these lists. You can get it as
>>> list( x[0].keys() )
Note also that the "elements" of a dictionary are actually the keys rather than the values. So you will also get the list ['id', 'number',...] if you write
>>> [ key for key in x[0] ]
or simply (and better):
>>> list( x[0] )
To get the first element is more tricky when x is not a list but a set or dict. In that case you can use next(x.__iter__()).
P.S.: You should actually think what you really want the keys to be -- a priori that should be the 'id's, not the 'number's, but your 'id's have duplicates which is contradictory to the concept and very definition / meaning of 'id' -- and then use the chosen keys as identifiers to index the elements of your collection 'x'. So if the keys are the 'number's, you should have a dictionary (rather than a list)
x = {123: {'id': 19, 'count': 1}, 23: {'id': 1, 'count': 7}, ...}
(where I additionally assumed that the numbers are indeed integers [which is more efficient] rather than strings, but that's up to you).
Then you can also do, e.g., x[123]['count'] += 1 to increment the 'count' of entry 123.
.keys() ... also, [ key for key in x[0] ] should just not be there, anything of the form [x for x in whatever] should just be list(whatever)
list ( [the dict] ).list( x[0] ) this does not show or "prove" that the result is indeed the keys of the dict, therefore I first wrote [ list( d.keys()) for d in x] to make it obvious and beyond any doubt, what the keys of the elements of his list of dicts (?!) are.You can use a list comprehension:
numbers = [dictionary.get('number') for dictionary in list_of_dictionaries]
dictionary['number'] in place of dictionary.get('number')Using a functional programming approach:
from operator import itemgetter
x_k = list(map(itemgetter('number'), x))
#[123, 23, 238, 9]
[i['number'] for i in x]