python pandas函数返回多个值并将其放入列中 [英] python pandas function return multiple values and put them into columns

问题描述

我有以下两个功能.第二个有效，但第一个无效.为什么?

i have two functions as below. The second one works but the first one doesn't work. Why?

import pandas as pd

df = pd.DataFrame(data = {'a': [1, 2, 3], 'b': [4, 5, 6]})

def add_subtract_list(a, b):
  return [1,2,3,4]
add_subtract_list(5,8)

df[['c','d','x','y']] = df.apply(
    lambda row: add_subtract_list(row['a'], row['b']), axis=1)

以下功能起作用.它来自此页面

below function works. It is from this page

import pandas as pd

df = pd.DataFrame(data = {'a': [1, 2, 3], 'b': [4, 5, 6]})



def add_subtract_list(a, b):
  return [a + b, a - b]

df[['sum', 'difference']] = df.apply(
    lambda row: add_subtract_list(row['a'], row['b']), axis=1)

推荐答案

更新您的函数，使其返回熊猫系列而不是python列表.

Update your function such that it returns a pandas Series instead of a python list.

def add_subtract_list(a, b):
  return pd.Series([1,2,3,4])

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