[英]Return next key of a given dictionary key, python 3.6+
我正在嘗試找到一種方法來獲取 Python 3.6+ 的下一個密鑰(已訂購)
例如:
dict = {'one':'value 1','two':'value 2','three':'value 3'}
我想要實現的是 function 返回下一個密鑰。 就像是:
next_key(dict, current_key='two') # -> should return 'three'
這是我到目前為止所擁有的:
def next_key(dict,key):
key_iter = iter(dict) # create iterator with keys
while k := next(key_iter): #(not sure if this is a valid way to iterate over an iterator)
if k == key:
#key found! return next key
try: #added this to handle when key is the last key of the list
return(next(key_iter))
except:
return False
return False
好吧,這是基本思想,我想我很接近,但是這段代碼給出了 StopIteration 錯誤。 請幫忙。
謝謝!
一種迭代方式...
def next_key(dict, key):
keys = iter(dict)
key in keys
return next(keys, False)
演示:
>>> next_key(dict, 'two')
'three'
>>> next_key(dict, 'three')
False
>>> next_key(dict, 'four')
False
while k:= next(key_iter)
沒有正確停止時循環。 使用iter
手動迭代可以通過捕獲StopIteration
來完成:
iterator = iter(some_iterable)
while True:
try:
value = next(iterator)
except StopIteration:
# no more items
或者通過將默認值傳遞給next
並讓它為您捕獲StopIteration
,然后檢查該默認值(但您需要選擇一個不會出現在您的可迭代對象中的默認值:):
iterator = iter(some_iterable)
while (value := next(iterator, None)) is not None:
# …
# no more items
但是迭代器本身是可迭代的,因此您可以跳過所有這些並使用普通的 ol' for 循環:
iterator = iter(some_iterable)
for value in iterator:
# …
# no more items
這轉化為您的示例:
def next_key(d, key):
key_iter = iter(d)
for k in key_iter:
if k == key:
return next(key_iter, None)
return None
您可以將字典的鍵作為列表獲取,並使用index()
獲取下一個鍵。 您還可以使用try/except
塊檢查IndexError
:
my_dict = {'one':'value 1','two':'value 2','three':'value 3'}
def next_key(d, key):
dict_keys = list(d.keys())
try:
return dict_keys[dict_keys.index(key) + 1]
except IndexError:
print('Item index does not exist')
return -1
nk = next_key(my_dict, key="two")
print(nk)
你最好不要使用dict
、 list
等作為變量名。
# Python3 code to demonstrate working of
# Getting next key in dictionary Using list() + index()
# initializing dictionary
test_dict = {'one':'value 1','two':'value 2','three':'value 3'}
def get_next_key(dic, current_key):
""" get the next key of a dictionary.
Parameters
----------
dic: dict
current_key: string
Return
------
next_key: string, represent the next key in dictionary.
or
False If the value passed in current_key can not be found in the dictionary keys,
or it is last key in the dictionary
"""
l=list(dic) # convert the dict keys to a list
try:
next_key=l[l.index(current_key) + 1] # using index method to get next key
except (ValueError, IndexError):
return False
return next_key
get_next_key(test_dict, '兩個')
'三'
get_next_key(test_dict, '三')
錯誤的
get_next_key(test_dict, '一個')
'二'
get_next_key(test_dict, '不存在')
錯誤的
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