'Last Key in Python Dictionary
I am having difficulty figuring out what the syntax would be for the last key in a Python dictionary. I know that for a Python list, one may say this to denote the last:
list[-1]
I also know that one can get a list of the keys of a dictionary as follows:
dict.keys()
However, when I attempt to use the logical following code, it doesn't work:
dict.keys(-1)
It says that keys can't take any arguments and 1 is given. If keys can't take arguments, then how can I denote that I want the last key in the list?
I am operating under the assumption that Python dictionaries are ordered in the order in which items are added to the dictionary with most recent item last. For this reason, I would like to access the last key in the dictionary.
I am now told that the dictionary keys are not in order based on when they were added. How then would I be able to choose the most recently added key?
Solution 1:[1]
It seems like you want to do that:
dict.keys()[-1]
dict.keys() returns a list of your dictionary's keys. Once you got the list, the -1 index allows you getting the last element of a list.
Since a dictionary is unordered*, it's doesn't make sense to get the last key of your dictionary.
Perhaps you want to sort them before. It would look like that:
sorted(dict.keys())[-1]
Note:
In Python 3, the code is
list(dict)[-1]
*Update:
This is no longer the case. Dictionary keys are officially ordered as of Python 3.7 (and unofficially in 3.6).
Solution 2:[2]
In python 3.6 I got the value of last key from the following code
list(dict.keys())[-1]
Solution 3:[3]
It doesn't make sense to ask for the "last" key in a dictionary, because dictionary keys are unordered. You can get the list of keys and get the last one if you like, but that's not in any sense the "last key in a dictionary".
Solution 4:[4]
Since python 3.7 dict always ordered(insert order),
since python 3.8 keys(), values() and items() of dict returns: view that can be reversed:
to get last key:
next(reversed(my_dict.keys()))
the same apply for values() and items()
PS, to get first key use:
next(iter(my_dict.keys()))
Solution 5:[5]
sorted(dict.keys())[-1]
Otherwise, the keys is just an unordered list, and the "last one" is meaningless, and even can be different on various python versions.
Maybe you want to look into OrderedDict.
Solution 6:[6]
There are absolutely very good reason to want the last key of an OrderedDict. I use an ordered dict to list my users when I edit them. I am using AJAX calls to update user permissions and to add new users. Since the AJAX fires when a permission is checked, I want my new user to stay in the same position in the displayed list (last) for convenience until I reload the page. Each time the script runs, it re-orders the user dictionary.
That's all good, why need the last entry? So that when I'm writing unit tests for my software, I would like to confirm that the user remains in the last position until the page is reloaded.
dict.keys()[-1]
Performs this function perfectly (Python 2.7).
Solution 7:[7]
You can do a function like this:
def getLastItem(dictionary):
last_keyval = dictionary.popitem()
dictionary.update({last_keyval[0]:last_keyval[1]})
return {last_keyval[0]:last_keyval[1]}
This not change the original dictionary! This happen because the popitem() function returns a tuple and we can utilize this for us favor!!
Solution 8:[8]
There's a definite need to get the last element of a dictionary, for example to confirm whether the latest element has been appended to the dictionary object or not.
We need to convert the dictionary keys to a list object, and use an index of -1 to print out the last element.
mydict = {'John':'apple','Mat':'orange','Jane':'guava','Kim':'apple','Kate': 'grapes'}
mydict.keys()
output: dict_keys(['John', 'Mat', 'Jane', 'Kim', 'Kate'])
list(mydict.keys())
output: ['John', 'Mat', 'Jane', 'Kim', 'Kate']
list(mydict.keys())[-1]
output: 'Kate'
Solution 9:[9]
this will return last element of dictionary:
dictObj[len(dictObj.keys()) - 1]
Solution 10:[10]
To find the last key of dictionary, use for loops with key , pass the loop and print the key,
#print last key
d1={"one":"first","two":"second","three":"third"}
for key in d1.keys():pass
print(key)
Solution 11:[11]
#to find last key:
dict = {'a':1,'b':2,'c':3,'d':4}
print(dict)
res = list(dict.key())[-1]
print(res)
#to find last value:
dict = {'a':1,'b':2,'c':3,'d':4}
print(dict)
res = list(dict.values())[-1]
print(res)
Sources
This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.
Source: Stack Overflow