Python数据分析 知识量:13 - 56 - 232
数据替换常用于处理缺失值、异常值。
一对一替换就是将某一个值替换为另一个值,使用replace()函数来实现。
对于repace(A,B)来说,表示将A替换为B。replace()函数默认情况下不会改变原数据对象,可以设置参数inplace=True来使替换对原数据对象生效,即改变原数据对象。
import pandas as pd df=pd.read_excel(r"D:\PythonTestFile\exam.xlsx") print(df,'\n') df['Sex'].replace('male','M',inplace=True) print(df)
运行结果为:
Name Sex Chinese English Math 0 Noah male 90 50 66 1 Emma female 56 56 55 2 Noah male 90 50 66 3 Olivia female 86 87 44 4 Liam male 55 88 69 5 Sophia female 90 66 96 6 Liam male 55 88 69 7 Isabella female 66 85 55 Name Sex Chinese English Math 0 Noah M 90 50 66 1 Emma female 56 56 55 2 Noah M 90 50 66 3 Olivia female 86 87 44 4 Liam M 55 88 69 5 Sophia female 90 66 96 6 Liam M 55 88 69 7 Isabella female 66 85 55
可以同时将多个值替换为一个值,同样使用replace()函数来实现,其参数中,被替换值以列表的形式给出。
import pandas as pd df=pd.read_excel(r"D:\PythonTestFile\exam.xlsx") print(df,'\n') df['Sex'].replace(['male','female'],'unknown',inplace=True) print(df)
运行结果为:
Name Sex Chinese English Math 0 Noah male 90 50 66 1 Emma female 56 56 55 2 Noah male 90 50 66 3 Olivia female 86 87 44 4 Liam male 55 88 69 5 Sophia female 90 66 96 6 Liam male 55 88 69 7 Isabella female 66 85 55 Name Sex Chinese English Math 0 Noah unknown 90 50 66 1 Emma unknown 56 56 55 2 Noah unknown 90 50 66 3 Olivia unknown 86 87 44 4 Liam unknown 55 88 69 5 Sophia unknown 90 66 96 6 Liam unknown 55 88 69 7 Isabella unknown 66 85 55
以上示例中,通过列表的形式给出被替换的值,将male和female都替换为unknown。
多对多替换其实就是多个一对一替换,同样使用replace()函数来实现,其参数中,被替换值与替换值以字典的形式给出。
import pandas as pd df=pd.read_excel(r"D:\PythonTestFile\exam.xlsx") print(df,'\n') df['Sex'].replace({'male':'M','female':'F'},inplace=True) print(df)
运行结果为:
Name Sex Chinese English Math 0 Noah male 90 50 66 1 Emma female 56 56 55 2 Noah male 90 50 66 3 Olivia female 86 87 44 4 Liam male 55 88 69 5 Sophia female 90 66 96 6 Liam male 55 88 69 7 Isabella female 66 85 55 Name Sex Chinese English Math 0 Noah M 90 50 66 1 Emma F 56 56 55 2 Noah M 90 50 66 3 Olivia F 86 87 44 4 Liam M 55 88 69 5 Sophia F 90 66 96 6 Liam M 55 88 69 7 Isabella F 66 85 55
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