python - 如何从字典中删除列表值？

Question

给定一个以列表作为值的字典。

myDict = {0: [0, 1, 2], 1: [], 2: [20, 25, 26, 28, 31, 34], 3: [], 4: [0, 1, 2, 3, 4, 7, 10], 5: [], 6: [10, 20, 24]}

如果值列表为空，如何从字典中删除项目？

我尝试遍历字典并删除项目，但在迭代期间不允许更改字典大小。

for item in myDict:
    if myDict[item] == []:
        print item
        del myDict[item]

Answer 1

使用字典理解:

>>> myDict = {0: [0, 1, 2], 1: [], 2: [20, 25, 26, 28, 31, 34], 3: [], 4: [0, 1, 2, 3, 4, 7, 10], 5: [], 6: [10, 20, 24]}
>>> myDict = {k: v for k, v in myDict.items() if v}
>>> myDict
{0: [0, 1, 2], 2: [20, 25, 26, 28, 31, 34], 4: [0, 1, 2, 3, 4, 7, 10], 6: [10, 20, 24]}

---

迭代时不允许添加、删除字典条目。制作 key 的副本以克服它。例如，在下面，我使用 tuple(myDict) 来获取键的副本。

>>> myDict =  {0: [0, 1, 2], 1: [], 2: [20, 25, 26, 28, 31, 34], 3: [], 4: [0, 1, 2, 3, 4, 7, 10], 5: [], 6: [10, 20, 24]}
>>> for item in tuple(myDict):
...     if myDict[item] == []:
...         del myDict[item]
...
>>> myDict
{0: [0, 1, 2], 2: [20, 25, 26, 28, 31, 34], 4: [0, 1, 2, 3, 4, 7, 10], 6: [10, 20, 24]}