pandas :SettingWithCopyWarning: [英] Pandas: SettingWithCopyWarning:

问题描述

我尝试了以下代码将列转换为日期":

I tried the following code to convert a column to "date":

df.['DATE'] =  pd.to_datetime(df['DATE'])

或

df.DATE =  pd.to_datetime(df.DATE)

但出现以下错误:

/Users/xyz/anaconda3/envs/sensor/lib/python3.6/site-packages/pandas/core/indexing.py:517: SettingWithCopyWarning:试图在一个副本上设置一个值 从DataFrame切片.尝试使用.loc [row_indexer，col_indexer] = 值代替

/Users/xyz/anaconda3/envs/sensor/lib/python3.6/site-packages/pandas/core/indexing.py:517: SettingWithCopyWarning: A value is trying to be set on a copy of a slice from a DataFrame. Try using .loc[row_indexer,col_indexer] = value instead

请参阅文档中的警告: http://pandas.pydata.org/pandas -docs/stable/indexing.html#indexing-view-versus-copy self.obj [item] = s

See the caveats in the documentation: http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy self.obj[item] = s

我将代码更改为以下内容:

I changed the code to the following:

df.loc[:,'DATE'] =  pd.to_datetime(df.loc[:,'DATE'])

但我仍然遇到相同的错误.

but I still get the same error.

与此相同

for i in df.index:
    df.loc[i,'DATE'] =  pd.to_datetime(df.loc[i,'DATE'])

推荐答案

您需要添加

You need add copy:

df = data.loc[data.ID == 79]

收件人:

df = data.loc[data.ID == 79].copy()

如果稍后在df中修改值，您会发现修改不会传播回原始数据(data)，并且Pandas会发出警告.

If you modify values in df later you will find that the modifications do not propagate back to the original data (data), and that Pandas does warning.

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