Using Python to extract specific data from a string

Question

GEYDCOR[R[G45DCMI,HA5DG],S[G[45DCNY,A5DCOI,E5D[CMI,M],I5DO,Q5DS,Y5DCMA],H[A5D[C[M[A,I,Q,Y],N[A,I,Q,Y],OA],G,I,K,M,O,Q,S],E5D[C[,M[A,I,Q,Y],N[A,I,Q,Y],O[A,I]],E[,M[A,I,Q,