A value is trying to be set on a copy of a slice from a DataFrame

import pandas as pd
def test1():
    data = [{'id':1,'name': '华为'},{'id':2,'name': '荣耀'}]
    frame = pd.DataFrame(data)
    for index in frame.index:
        # frame['name'][index] = '华为' #这样写报错误
        frame.loc[index,'name'] = '华为' #这样写不报错误
def test2():
    data = [{'id':'1','name': '华为'},{'id':'2','name': '荣耀'}]
    frame = pd.DataFrame(data)
    for index in frame.index:
        frame['name'][index] = '华为' #这样写不报错误 可能因为frame中都是object类型吧
        frame.loc[index,'name'] = '华为' #这样写不报错误
def test3():
    data = [{'name': '华为','rate':9.9},{'name': '荣耀','rate':9.5}]
    frame = pd.DataFrame(data)
    for index in frame.index:
        # frame['name'][index] = '华为' #这样写报错误
        frame.loc[index,'name'] = '华为' #这样写不报错误
if __name__ == '__main__':    
    test1()
    test2()
    test3()

使用frame.loc[index,'name']就没有问题了。

type(frame)
<class 'pandas.core.frame.DataFrame'>
RangeIndex: 2 entries, 0 to 1
Data columns (total 3 columns):
id     2 non-null int64
rate    1 non-null float64
name     2 non-null object
dtypes: float64(1), int64(1), object(1)
memory usage: 128.0+ bytes


.\test.py:34: SettingWithCopyWarning:
A value is trying to be set on a copy of a slice from a DataFrame

See the caveats in the documentation: http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy

本文地址：https://blog.csdn.net/zycdn/article/details/107361720