嵌套for循環使用List Comprehension進行多個操作

Question

只是理解列表理解，就像在最近的一次采訪中，技術人員問我這個問題，並且作為一個自學者我回答了lambda，這不是列表理解。

假設我們有一個時間序列數據“Shiller”， http：//us.spindices.com/indices/real-estate/sp-corelogic-case-shiller-us-national-home-price-nsa-index

我使用以下循環計算了aic / bic：

shiller = [please use some random data or use the link above]

import matplotlib.pyplot as plt
import statsmodels.api as sm
import pandas as pd

def aicbic(shiller):
  arimaijk = []
  aicijk = []
  bicijk = []
  index = []
  for i in range(1,3):
      for j in range(1,2):
          for k in range(0,5):
              arimaijk.append(sm.tsa.ARIMA(shiller,(i,j,k)).fit())
              index.append([i,j,k])
              aicijk.append(arimaijk[k].aic)            
              bicijk.append(arimaijk[k].bic)
  return aicijk, bicijk

aicbic(shiller)
Out[9]: 
([-235.77314152121426,-233.9375761653174,-233.3841011331017,-241.65994870973782,-240.2975620564456,-235.77314152121426,-233.9375761653174,-233.3841011331017,-241.65994870973782,-240.2975620564456],
 [-227.98778197081049,-223.55709676477906,-220.40850188242874,-226.08922960893028,-222.13172310550345,-227.98778197081049,-223.55709676477906,-220.40850188242874,-226.08922960893028,-222.13172310550345])

現在，我想使用List Comprehension這個結果，所以我寫了以下行，它們返回錯誤：

def aicbic(data):    
  arimaijk = []
  aicijk = []
  bicijk = []
  index = []
  [(sm.tsa.ARIMA(data,(i,j,k)).fit(),index.append([i,j,k]),\
  aicijk.append(arimaijk[k].aic),bicijk.append(arimaijk[k].bic)) \
  for i in range(1,3) for j in range(1,2) for k in range(0,5)]

IndexError：列表索引超出范圍

Answer 1

該錯誤與列表理解本身無關：

[(sm.tsa.ARIMA(data,(i,j,k)).fit(),index.append([i,j,k]),\
  aicijk.append(arimaijk[k].aic),bicijk.append(arimaijk[k].bic)) \
  for i in range(1,3) for j in range(1,2) for k in range(0,5)]

引發錯誤IndexError: list index out of range是因為你想訪問arimaijk[k]而arimaijk是一個空列表（ aicbic(data)函數的第一行是arimaijk=[] ）。

Answer 2

您的函數使用itertools和list comprehensions重新設置：

碼：

import itertools as it

def aicbic(shiller):
    loop = list(it.product(range(1, 3), range(1, 2), range(0, 5)))
    arimaijk = [sm.tsa.ARIMA(shiller, (i, j, k)).fit() for i, j, k in loop]
    aicijk = [arimaijk[k].aic for i, j, k in loop]
    bicijk = [arimaijk[k].bic for i, j, k in loop]
    return aicijk, bicijk

測試代碼：

result = aicbic(shiller)

import numpy as np
assert np.all(np.isclose(result, (
    [-235.77314152121426, -233.9375761653174, -233.3841011331017,
     -241.65994870973782, -240.2975620564456, -235.77314152121426,
     -233.9375761653174, -233.3841011331017, -241.65994870973782,
     -240.2975620564456],
    [-227.98778197081049, -223.55709676477906, -220.40850188242874,
     -226.08922960893028, -222.13172310550345, -227.98778197081049,
     -223.55709676477906, -220.40850188242874, -226.08922960893028,
     -222.13172310550345]
)))

注意：

你可能有某種bug，因為aicijk和bicijk只依賴於k 。

Answer 3

感謝Hossein，我想現在我知道如何使用List Comprehensions了！

def aicbic(data):
  arimaijk = []
  aicijk = []
  bicijk = []
  index = []
  [(arimaijk.append(sm.tsa.ARIMA(data,(i,j,k)).fit()),index.append([i,j,k]),\
  aicijk.append(arimaijk[k].aic),bicijk.append(arimaijk[k].bic)) \
  for i in range(1,3) for j in range(1,2) for k in range(0,5)]
  return aicijk, bicijk


result = aicbic(shiller)