我在Pandas（2.0.1）DataFrame中有四个类型为object的列，它们希望转换为int。
应用以下方法：

cols = ['x1','x2','y1','y2']

df[cols] = df[cols].apply(pd.to_numeric)

# The same message is raised when trying to cast a single column:
df['x1'] = pd.to_numeric(df['x1'])

# The same message is also raised when using .astype():
dff[cols] = dff[cols].astype(int)

如本文所述：https://stackoverflow.com/a/28648923/6630397引发消息：

/tmp/ipykernel_87959/2834796204.py:1: 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
    
See the caveats in the documentation:
https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html#returning-a-view-versus-a-copy
df[cols] = df[cols].apply(pd.to_numeric)

如何正确地（快速地）将四列从object转换为int？