英文:
Obtain specific key from python dictionary based on index
问题
我需要确定特定索引指向两个字典中的哪个对象（在这种情况下是图像数组）。
dict_count 表示我有 400 个对象 1，300 个对象 2 等等。
dict_object 包含对象（最大计数在 dict_count 中提到）
现在，如果我给定一个索引 = 450，我需要从 dict_object 中获取 '标签 2' 下的第 50 个对象。
现有代码（可能不是有效的）
Matrix = [[-1 for x in range(sum(dict_count.values()))] for y in range(2)]
i = 0
index = 450
for k in dict_object.keys():
for images in dict_object[k]:
Matrix[0][i] = images
Matrix[1][i] = k
i += 1
obj = Matrix[index-1][0]
label = MAtrix[index-1][1]
如何有效地执行这个任务？ TIA!
英文:
I need to identify which object(image array in this case) a particular index points to from two dictionaries.
dict_count = {1: 400, 2:300, 3:200, 4: 100}
dict_count says I have 400 of object 1, 300 of object 2 and so on.
dict_object = {1 :[obj1, obj2 ... obj400], 2 :[obj1, obj2 ...obj300], 3 :[obj1, obj2 ...], 4 :[obj1, obj2 ...]
dict_object contains the objects (max count is mentioned in dict_count)
Now, if I am given an index = 450, I need to get the 50th object under 'label 2' from the dict_object.
Existing code (probably not efficient)
Matrix = [[-1 for x in range(sum(dict_count.values()))] for y in range(2)]
i = 0
index = 450
for k in dict_object.keys():
for images in dict_object[k]:
Matrix[0][i] = images
Matrix[1][i] = k
i += 1
obj = Matrix[index-1][0]
label = MAtrix[index-1][1]
How do I do this efficiently? TIA!
答案1
得分: 3
不要迭代一次一个索引，而是通过dict_count进行分块迭代：
def get_obj(i):
for k, c in dict_count.items():
if i < c:
return dict_object[k][i]
else:
i -= c
raise IndexError(f"索引 {i} 超出 {sum(dict_count.values())}")
英文:
Rather than iterating through indices 1 at a time, iterate through dict_count so you can do it in chunks:
def get_obj(i):
for k, c in dict_count.items():
if i < c:
return dict_object[k][i]
else:
i -= c
raise IndexError(f"index {i} exceeds {sum(dict_count.values())}")
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