pandas的apply函数使用

参考博客
https://blog.csdn.net/weixin_42512684/article/details/107461383

测试案例1

import numpy as np
import pandas as pd 
x=np.array([[1,2,3],[2,3,4],[1,2,2],[1,2,2]])
df=pd.DataFrame(x)
print(df)

对某一列进行操作

import pandas as pd
import numpy as np
from sklearn import datasets

iris = datasets.load_iris()

data = pd.concat([pd.DataFrame(iris.target, columns = ['target']), pd.DataFrame(iris.data, columns = iris.feature_names)], axis = 1)

def target_replace(x):
    for i in [0,1,2]:
        if x == i:
            return(iris.target_names[i]) # 对某一类进行操作

测试案例3

自定义apply函数，传入的参数都是dataframe,并不是一个pd.Series