英文:
switching key and values for values and keys in dictionary doesn't work properly
问题
我正在尝试计算具有不同邻居数量的节点出现次数，从一个边列表中获取，这在切换键和值时出现问题，元素会丢失，尽管在其他列表上运行正常，但在这个列表上它没有给出完整的输出。缺少什么？
[(0, 4), (1, 4), (2, 0), (3, 2), (4, 3)]
{0: 2, 4: 3, 1: 1, 2: 2, 3: 2}
Counter({2: 3, 3: 1, 1: 1})
{3: 2, 1: 1} # 这里是错误的
count_occurances = Counter(occurances.values())
f = dict((v, k) for k, v in count_occurances.items())
期望的输出是
{3: 2, 1: 3}
英文:
I'm trying to count the occurances for nodes with number of neighbors from an edge list which is working except when I want to switch between keys and values, elements get lost, although it's working on other lists but this one it's not giving the entire output. what's missing?
[(0, 4), (1, 4), (2, 0), (3, 2), (4, 3)]
{0: 2, 4: 3, 1: 1, 2: 2, 3: 2}
Counter({2: 3, 3: 1, 1: 1})
{3: 2, 1: 1} # here is wrong
count_occurances = Counter(occurances.values())
f = dict((v, k) for k, v in count_occurances.items())
the expected output is
{3: 2, 1:3, 1: 1}
答案1
得分: 1
The Counter构造函数没有错。当你给它一个具有items方法的参数时，它会直接将其转换为键:计数对（字典不进行总计操作）:
D = {2: 3, 3: 1, 1: 1}
C = Counter(D)
# C --> Counter({2: 3, 3: 1, 1: 1})
要颠倒计数器的值和键，你需要使用列表作为值，以便重复计数可以存储它们的所有键。
R = dict()
R.update((count, R.get(count, []) + [key]) for key, count in C.items())
# R --> {3: [2], 1: [3, 1]}
英文:
The Counter constructor is not wrong. When you give it a parameter that has an items method, it converts it directly to the key:count pairs (no totalling operation occurs for a dictionary):
D = {2: 3, 3: 1, 1: 1}
C = Counter(D)
# C --> Counter({2: 3, 3: 1, 1: 1})
To reverse the counter's values and keys, you'll need to use lists as values so that duplicate counts can store all of their keys.
R = dict()
R.update( (count,R.get(count,[])+[key]) for key,count in C.items() )
# R --> {3: [2], 1: [3, 1]}
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