Setting with copy warning

[catlessness]

Why am I getting the "setting with copy" warning with the code below? Am I not doing what they suggested? And the result is wrong so I guess there is some problem with this.

import pandas as pd
'''
...
'''
#dfout is a pd.DataFrame instance
dfout.columns=[0,1,2]
dfout.loc[:,3]=dfout.loc[:,0]
dfout.loc[:,4]=dfout.loc[:,1]
dfout.loc[:,5]=dfout.loc[:,2]
dfout.loc[:,6]=np.sqrt(dfout.loc[:,4]**2+dfout.loc[:,5]**2)
dfout.loc[:,7]=np.arctan(dfout.loc[:,5]/dfout.loc[:,4])/np.pi*360

Thanks