谁能解释一下 Pandas 中的 SettingWithCopyWarning 是什么 [duplicate]

问：

我是熊猫的新手，在为我的课程做作业时，我遇到了一个警告，上面写着

e:\Python.py\coursera_data\1_week3_assign.py:10: SettingWithCopyWarning: 
A value is trying to be set on a copy of a slice from a DataFrame

我想知道这到底是什么意思？我必须更改我的代码吗？

法典

import pandas as pd
import numpy as np
import re
csv=pd.read_excel('Energy Indicators.xls',skiprows=17,usecols=[2,3,4,5],skipfooter=1)
csv=csv.rename(columns={'Unnamed: 2':'Country','Petajoules':'Energy Supply','Gigajoules':'Energy Supply per Capita','%':'% Renewable'})
csv['Energy Supply'].replace(['...'],[np.nan],inplace=True)
for i in range(227):
    csv['Country'][i]=re.sub(pattern='\(.*?\)',repl='',string=csv['Country'][i])
    csv['Country'][i]=re.sub(pattern='\d',repl='',string=csv['Country'][i])
csv['Energy Supply']=csv['Energy Supply']*1000000
print(csv.head()) 

完整的警告消息

e:\Python.py\coursera_data\1_week3_assign.py:8: SettingWithCopyWarning: 
A value is trying to be set on a copy of a slice from a DataFrame

See the caveats in the documentation: https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html#returning-a-view-versus-a-copy
  csv['Country'][i]=re.sub(pattern='\(.*?\)',repl='',string=csv['Country'][i])
e:\Python.py\coursera_data\1_week3_assign.py:9: SettingWithCopyWarning: 
A value is trying to be set on a copy of a slice from a DataFrame
See the caveats in the documentation: https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html#returning-a-view-versus-a-copy
  csv['Country'][i]=re.sub(pattern='\d',repl='',string=csv['Country'][i])