在列表字典中按值获取键 -python

Question

我有一个包含键的字典，同时键包含特定的整数列表。我想构建一个字典，将值显示为键，而这个新字典的值将是包含先前值的先前键的列表。例如，我有：

turns

{'Monday_2022_03_14': [25, 17, 2, 32, 43, 40, 23, 7, 19, 16],
 'Tuesday_2022_03_15': [33, 10, 16, 31, 25, 22, 43, 41, 21, 28, 3, 30, 29],
 'Wednesday_2022_03_16': [19, 27, 40, 3, 9, 2, 14, 21, 44, 17],
 'Thursday_2022_03_17': [16, 23, 1, 30, 29, 44, 5, 42, 27, 19],
 'Friday_2022_03_18': [6, 17, 2, 29, 27, 41, 44, 5, 40, 42]}

我想举个例子：

{1:['Thursday_2022_03_17'],
 2:['Monday_2022_03_14','Wednesday_2022_03_16','Friday_2022_03_18'],
 3:['Tuesday_2022_03_15','Wednesday_2022_03_16],
 ...}  #and so on

我试图在循环中实现下一个解决方案（我在 Get key by value in dictionary 中找到了它），但后来我意识到这只能在只有一个值的键的字典中工作，而不是像我这样的列表：

list(turns.keys())[list(turns.values()).index(16)]
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
~\AppData\Local\Temp/ipykernel_19168/930684082.py in <module>
----> 1 list(turns.keys())[list(turns.values()).index(16)]

ValueError: 16 is not in list

如果你不提供循环解决方案也没关系，我可以实现它，但我需要帮助按值获取键名（如上面的行），但重点是列表而不是简单的值。

感谢大家。

Answer 1

一种方法是使用 dict.setdefault 并迭代列表：

out = {}
for k, lst in turns.items():
    for v in lst:
        out.setdefault(v, []).append(k)

然后如果你想要字典按键排序，你可以使用sorted:

out = {k: out[k] for k in sorted(out)}

输出：

{1: ['Thursday_2022_03_17'],
 2: ['Monday_2022_03_14', 'Wednesday_2022_03_16', 'Friday_2022_03_18'],
 3: ['Tuesday_2022_03_15', 'Wednesday_2022_03_16'],
 5: ['Thursday_2022_03_17', 'Friday_2022_03_18'],
 6: ['Friday_2022_03_18'],
 7: ['Monday_2022_03_14'],
 9: ['Wednesday_2022_03_16'],
 10: ['Tuesday_2022_03_15'],
 14: ['Wednesday_2022_03_16'],
 16: ['Monday_2022_03_14', 'Tuesday_2022_03_15', 'Thursday_2022_03_17'],
 17: ['Monday_2022_03_14', 'Wednesday_2022_03_16', 'Friday_2022_03_18'],
 19: ['Monday_2022_03_14', 'Wednesday_2022_03_16', 'Thursday_2022_03_17'],
 21: ['Tuesday_2022_03_15', 'Wednesday_2022_03_16'],
 22: ['Tuesday_2022_03_15'],
 23: ['Monday_2022_03_14', 'Thursday_2022_03_17'],
 25: ['Monday_2022_03_14', 'Tuesday_2022_03_15'],
 27: ['Wednesday_2022_03_16', 'Thursday_2022_03_17', 'Friday_2022_03_18'],
 28: ['Tuesday_2022_03_15'],
 29: ['Tuesday_2022_03_15', 'Thursday_2022_03_17', 'Friday_2022_03_18'],
 30: ['Tuesday_2022_03_15', 'Thursday_2022_03_17'],
 31: ['Tuesday_2022_03_15'],
 32: ['Monday_2022_03_14'],
 33: ['Tuesday_2022_03_15'],
 40: ['Monday_2022_03_14', 'Wednesday_2022_03_16', 'Friday_2022_03_18'],
 41: ['Tuesday_2022_03_15', 'Friday_2022_03_18'],
 42: ['Thursday_2022_03_17', 'Friday_2022_03_18'],
 43: ['Monday_2022_03_14', 'Tuesday_2022_03_15'],
 44: ['Wednesday_2022_03_16', 'Thursday_2022_03_17', 'Friday_2022_03_18']}

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