Does the keys() function return dictionary keys in any specific order?
No, there is no guaranteed order for the list of keys returned by the keys() function. In most cases, the key list is returned in the same order as the insertion, however, that behavior is NOT guaranteed and should not be depended on by your program. A common practice is to pass keys() to the sorted() function to ensure that the list of keys is sorted before iteration.
The order is indeed not guaranteed in Python 3.5 and earlier, but is the same as the insertion order (although not documented), in Python 3.6, and documented in 3.7 and beyond.
How would the sorted() function be used? Do you have some sample code?
can i know whatâs wrong in my solution ?
sorted_keys = sorted(my_dict.keys())
You simply want the following on line 4:
users = user_ids.keys()
and eliminate the loop on lines 6-7.
and what it the differs between the answer on the example
for student in test_scores.keys():
print(student)
and the answer on the test
users = user_ids.keys()
print(users)
and why we canât use the first answer
In the exercise you are referring to, we are asked to create a variable containing the keys of a dictionary and to then print this variable. Which steps are (not) performed in the two code snippets you provide?
In what way is the list sorted?
I canât see it being sorted alphabetically or by value nor length of word.
There are parentheses after keys. Does It mean we can choose some specific keys?
If we want to choose specific keys do we have to iterate over the keys.
Keys is a method and therefore requires the function style parantheses to call it: .keys() but it doesnât take any arguments.Specific keys can be accessed with the dict[key] syntax so it isnât necessary to iterate through them (the look-up is done for you). For multiple specific keys you would need some sort of looping/mapping/unpacking or similar but itâs not the ideal way to use dictionaries.
what you are trying to get is a âlist of name of keysâ but expected result is a âlist of dictionary keysâ.
your result is not matching the expected result.
Also, the example doesnât fill an empty list with a for statement. To execute the code you wrote, you would need to use .append instead of += (which works on strings, but not lists?). Correct me if Iâm wrong.
Since Python 3.7 was released as per my undestanding, dictionaries now return keys in order.
As the error says, it is expecting a dict_keys type but your solution is outputting the list type.
i donât understand is it in order in python 3.7 and later or not ?
The mention of Python 3.6 was an implementation detail of CPython3.6; it technically followed an order but it had the potential to change in future releases and the program may misbehave if run with non CPython versions (Jython, PyPy etc.). Relying on implementation details has always been considered bad practice (liable to change, less portable etc. etc.).
With Python 3.7 a dict was guaranteed to be insertion ordered (order based on when items are added) as part of the Python language specification and this should be true of any implementation of Python from 3.7 onwards.
Thank you very much i have understood
Use append() instead +=. And replace square brackets from âiâ.
a = {"a": 1, "b": 2, "d": 4, "c": 3, "e": 5, "f": 6}
b = []
for i in a.keys():
b.append(i)
print(b)
Since .keys() is already an enumerable, we can transform it to a list with the splat operatorâŚ
>>> a = {"a": 1, "b": 2, "d": 4, "c": 3, "e": 5, "f": 6}
>>> b = [*a.keys()]
>>> b
['a', 'b', 'd', 'c', 'e', 'f']
>>> c = [*a.values()]
>>> c
[1, 2, 4, 3, 5, 6]
>>> d = [*a.items()]
>>> d
[('a', 1), ('b', 2), ('d', 4), ('c', 3), ('e', 5), ('f', 6)]