pandas srt.lower()不适用于数据框列 [英] pandas srt.lower() not working on dataframe column

问题描述

我正在使用Kaggle提供的Titanic数据集.我在一个数据帧中有它，我想将性别"列的大小写更改为小写.我正在使用以下代码

I'm working with the Titanic dataset available from Kaggle. I have it in a dataframe and i want to change the case of the "sex" column to lowercase. I'm using the following code

import pandas as pd

df = pd.read_csv('titanic.csv')
print dfFull['sex'].unique()
df.sex.str.lower()

#check if it worked
print df['sex'].unique()

并尝试

df['sex'].str.lower()

但是当我运行df['sex'].unique()时，我得到三个唯一值[male, female, Female].

but when I run df['sex'].unique() I get three unique values [male, female, Female].

为什么我的代码不降低字符串的大小写并将其保存回数据帧，以便从.unique方法获得[male, female]的值?

Why does my code not lower the case of the strings and save it back to the dataframe so i get [male, female] of from the .unique method?

推荐答案

str.lower()不会修改现有列.它只是返回一个应用了小写转换的新Series.如果要覆盖原始列，则需要将结果分配回它:

str.lower() does not modify the existing column. It just returns a new Series with the lowercase transform applied. If you want to overwrite the original column, you need to assign the result back to it:

df['sex'] = df.sex.str.lower()

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