Python Pandas:与apply()一起使用时功能不起作用 [英] Python Pandas: Function doesn't work when used with apply()

问题描述

以下功能:

def func(x):
    for k in x['slices']:
        for j in k:
            print(x['low'].iloc[j]) 

以以下方式应用将起作用:

applied in the following manner works:

func(test)

但是如下却没有:

test.apply(func, axis=1)

您能确定原因吗?

我仅将打印用于调试目的: 该功能曾经是:

I used the print only for debug purpose: the function used to be :

def func(x):
    result=[]
    for k in x:
        for j in k:    
            result.append(x['low'].iloc[j])
    return result

这也不起作用

在元素下方重建数据.

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

   dict = {'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, 2, None)],
      1: [slice(1, 3, None), slice(2, 3, None)],
      2: [slice(1, 4, None), slice(2, 4, None), slice(3, 4, None)],
      3: [slice(1, 5, None),
       slice(2, 5, None),
       slice(3, 5, None),
       slice(4, 5, None)],
      4: [slice(1, 6, None),
       slice(2, 6, None),
       slice(3, 6, None),
       slice(4, 6, None),
       slice(5, 6, None)],
      5: [slice(1, 7, None),
       slice(2, 7, None),
       slice(3, 7, None),
       slice(4, 7, None),
       slice(5, 7, None),
       slice(6, 7, None)],
      6: [slice(1, 8, None),
       slice(2, 8, None),
       slice(3, 8, None),
       slice(4, 8, None),
       slice(5, 8, None),
       slice(6, 8, None),
       slice(7, 8, None)]}}

推荐答案

以这种方式定义函数

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

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