Questions related to Python's dictionary views created with the keys, items and values methods (viewkeys, viewitems and viewvalues on Python 2.7)
Questions tagged [dictview]
13 questions
67
votes
3 answers
dict.keys()[0] on Python 3
I have this sentence:
def Ciudad(prob):
numero = random.random()
ciudad = prob.keys()[0]
for i in prob.keys():
if(numero > prob[i]):
if(prob[i] > prob[ciudad]):
ciudad = i
else:
…
Menticolcito
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- 1
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- 11
8
votes
2 answers
Python: Understanding dictionary view objects
I've been trying to understand built-in view objects return by .items(), .values(), .keys() in Python 3 or similarly by .viewitems(), .viewvalues(), .viewkeys(). There are other threads on that subject but none (even the doc) seems to described how…
scharette
- 9,437
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- 67
4
votes
2 answers
Why exactly are .values() and .keys() considered O(1)?
Couldnt track down a solid enough reasoning for why dictionary functions such as .values() and .keys() are considered to be O(1) in big O notation. (not sure if .items() is also considered O(1) )
Vanessa Ventura
- 99
- 1
- 9
4
votes
1 answer
Why does dict unioned with dict.keys() return a set?
As I originally expected, the union of a dict and a set gives TypeError:
>>> {1:2} | {3}
Traceback (most recent call last):
File "", line 1, in
TypeError: unsupported operand type(s) for |: 'dict' and 'set'
However, surprisingly,…
Andrew Sun
- 4,101
- 6
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- 53
3
votes
1 answer
Do Python 2.7 views, for/in, and modification work well together?
The Python docs give warnings about trying to modify a dict while iterating over it. Does this apply to views?
I understand that views are "live" in the sense that if you change the underlying dict, the view automatically reflects the change. I'm…
Ouroborus
- 16,237
- 4
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- 62
2
votes
2 answers
python3: sum (union) of dictionaries with "+" operand raises exception
I'd like to avoid the update() method and I read that is possible to merge two dictionaries together into a third dictionary using the "+" operand, but what happens in my shell is this:
>>> {'a':1, 'b':2}.items() + {'x':98, 'y':99}.items()
Traceback…
etuardu
- 5,066
- 3
- 46
- 58
2
votes
1 answer
Why do set operators work with dict_key view objects but not the equivalent set methods?
Edit: Possible duplicate. Only after posting this question and looking in "related questions" was I able to find Why are set methods like .intersection() not supported on set-like objects?, this question may similar enough to be a duplicate.
I am…
johnDanger
- 1,990
- 16
- 22
2
votes
2 answers
Why are set methods like .intersection() not supported on set-like objects?
In Python 3.7, I'd like to calculate the intersection of two dictionaries' keys. To do this, I'd like to call the .intersection() method on their keys(), however it does not work.
.keys() produces a set-like object, however most set methods don't…
hyperknot
- 13,454
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- 153
2
votes
1 answer
Comparing lists with dictviews
Dictionary views "are set-like objects" and can thus be used to compare dictionary contents with other objects. Specifically,
key-views: set-like
value-views: not set-like
item-views: set-like if (key, value) pairs are unique and hashable
The…
pylang
- 40,867
- 14
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- 121
2
votes
1 answer
dictionary lookup on Python 2.7 vs 3.4
This came up in a nitpick discussion about the prefered style for iterating over dictionary keys if you need to apply some test to the value. I was comparing the performance of [k for k in d if d[k] == 1] against [k for k, v in d.items() if v ==…
Paulo Scardine
- 73,447
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- 153
2
votes
4 answers
Inconsistent behaviour between dict.items and dict.values
Note: code examples in python3, but the question stands for python2 as well (replacing .keys with .viewkeys, etc)
dict objects provide view methods which (sometimes) support set operations:
>>> {'a': 0, 'b': 1}.keys() & {'a'}
{'a'}
>>> {'a': 0, 'b':…
wim
- 338,267
- 99
- 616
- 750
1
vote
3 answers
How to compare values of two dictionaries with list comprohension?
How to compare only the values of two dictonaries?
So I have this:
dict1 = {"appe": 3962.00, "waspeen": 3304.08}
dic2 = {"appel": 3962.00, "waspeen": 3304.08}
def compare_value_dict(dic):
return dic
def compare_value_dict2(dic2):
…
mightycode Newton
- 3,229
- 3
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- 54
1
vote
0 answers
dict_key and dict_value to list performances
With python 2.x we can do this:
>>> d = {0:'foo', 1:'bar'}
>>> d.keys()
[0, 1]
>>> d.keys()[0]
0
>>> d.values()
['foo', 'bar']
>>> d.values()[0]
'foo'
With python 3.x, .keys() return dict_key and .values() return dict_value. I guess these view…
bux
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