通过字典的键进行迭代，并对作为数据帧的值进行切片

Question

我有一本字典，其值为“ pandas data frame”。
我想遍历键并对键的值执行切片。

dictionary = {'key_1':[[1, 2, 3, 4], [4, 6, 7, 8]], 'key_2': [[5,8,4,6],[1,5,2,6]]}  

最终输出如下所示：

dictionary = {'key_1':[[3,4],[7,8]], 'key_2': [[4,6], [2,6]]}  

任何帮助，将不胜感激。

Answer 1

假设我们有一个清单：

li = [1, 2, 3, 4]

...，如果我们需要最后两个元素：

li[-2:] ==> [3, 4]

嵌套列表如何：

v = [[1, 2, 3, 4], [4, 6, 7, 8]]
[li[-2:] for li in v] ==> [[3, 4], [7, 8]

把它放在一起：

{k: [li[-2:] for li in v] for k, v in dictionary.items()}  # It's what you want

Answer 2

您可以借助nested for loop和dict.items()方法获得所需的结果，如下所示：

dictionary = {'key_1':[[1, 2, 3, 4], [4, 6, 7, 8]], 'key_2': [[5,8,4,6],[1,5,2,6]]} 
new_dict = {}

for key,value in dictionary.items():  # Iterating key and value
    my_list = []
    for var in value:   # Iterating over a particular value
        my_list.append( var[-1:-3:-1]  )  # Performing indexing and slicing.
    new_dict[key] = my_list   
dictionary = new_dict
print(dictionary)

输出量

{'key_1': [[4, 3], [8, 7]], 'key_2': [[6, 4], [6, 2]]}

希望对您有帮助。