Pandas KeyError：值不在索引中 [英] Pandas KeyError: value not in index

问题描述

我有以下代码，

df = pd.read_csv(CsvFileName)

p = df.pivot_table(index=['Hour'], columns='DOW', values='Changes', aggfunc=np.mean).round(0)
p.fillna(0, inplace=True)

p[["1Sun", "2Mon", "3Tue", "4Wed", "5Thu", "6Fri", "7Sat"]] = p[["1Sun", "2Mon", "3Tue", "4Wed", "5Thu", "6Fri", "7Sat"]].astype(int)

它始终有效，直到csv文件没有足够的覆盖率（所有工作日）。例如，使用以下.csv文件，

It has always been working until the csv file doesn't have enough coverage (of all week days). For e.g., with the following .csv file,

DOW,Hour,Changes
4Wed,01,237
3Tue,07,2533
1Sun,01,240
3Tue,12,4407
1Sun,09,2204
1Sun,01,240
1Sun,01,241
1Sun,01,241
3Tue,11,662
4Wed,01,4
2Mon,18,4737
1Sun,15,240
2Mon,02,4
6Fri,01,1
1Sun,01,240
2Mon,19,2300
2Mon,19,2532

我会收到以下错误：

KeyError: "['5Thu' '7Sat'] not in index"

它似乎有一个非常简单的修复方法，但我对Python来说太新了知道如何解决它。请帮忙。谢谢。

It seems to have a very easy fix, but I'm just too new to Python to know how to fix it. Please help. Thanks.

推荐答案

使用 reindex 获取所需的所有列。它会保留已存在的那些，否则放入空列。

use reindex to get all columns you need. It'll preserve the ones that are already there and put in empty columns otherwise.

p = p.reindex(columns=['1Sun', '2Mon', '3Tue', '4Wed', '5Thu', '6Fri', '7Sat'])

所以你的整个代码示例应如下所示：

So your entire code example should look like this:

df = pd.read_csv(CsvFileName)

p = df.pivot_table(index=['Hour'], columns='DOW', values='Changes', aggfunc=np.mean).round(0)
p.fillna(0, inplace=True)

columns = ["1Sun", "2Mon", "3Tue", "4Wed", "5Thu", "6Fri", "7Sat"]
p = p.reindex(columns=columns)
p[columns] = p[columns].astype(int)

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