Python Pandas : Table manipulation with slices as variables

Question

我有一个表格，例如follow(黑色)。我想创建一个附加列，例如右侧可见的红色列。基本上，对于“切片”列中的每个切片变量，我想从“低”列中检索相应的值。

我已经尝试了无数种方法来做到这一点，我已经在这里发布了一个问题，试图解决我认为可行的方法之一:

Python Pandas: Function doesn't work when used with apply()

该问题的一位受访者建议我只是问如何实现它，因此我在这里。

我还在下面重新发布了重建该数据帧的代码:

df = pd.DataFrame(dict, columns=["low", "slices"])

  {'low': {0: 1207.25,
  1: 1207.5,
  2: 1205.75,
  3: 1206.0,
  4: 1201.0,
  5: 1202.75,
  6: 1203.75},
 'slices': {0: [slice(1, 1, None)],
  1: [slice(1, 2, None), slice(2, 2, None)],
  2: [slice(1, 3, None), slice(2, 3, None), slice(3, 3, None)],
  3: [slice(1, 4, None),
   slice(2, 4, None),
   slice(3, 4, None),
   slice(4, 4, None)],
  4: [slice(1, 5, None),
   slice(2, 5, None),
   slice(3, 5, None),
   slice(4, 5, None),
   slice(5, 5, None)],
  5: [slice(1, 6, None),
   slice(2, 6, None),
   slice(3, 6, None),
   slice(4, 6, None),
   slice(5, 6, None),
   slice(6, 6, None)],
  6: [slice(1, 7, None),
   slice(2, 7, None),
   slice(3, 7, None),
   slice(4, 7, None),
   slice(5, 7, None),
   slice(6, 7, None),
   slice(7, 7, None)]}}

Answer 1

这样定义你的函数

def fun(slices):
    return [df.low.loc[s].tolist() for s in slices]

并应用于切片列

df['slices_low'] = df.slices.apply(fun)

df