|  1 |    initial version    |  
As @slelievre suggested, you should provide a concrete example, so that we can provide a more adapted answer.
Note that if M is you matrix,  you can change the ring on which it is defined as follows (CDF stands for Complex Double Field):
sage: N = M.change_ring(CDF)
 Then, you can ask for the eigenvalues and eigenvectors of N.
 
                
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