def main(): A=[0]*4 X=A*4 B=[A]*4 C=[A[:]]*4 D=[[0]*4]*4 print("A=",A) print("X=",X) print("B=",B) print("C=",C) print("D=",D) B[1][1]=2 print("B=",B) C[1][1]=2 print("C=",C) D[1][1]=2 print("D=",D) print("B[1]=",B[1]) print("C[1]=",C[1]) print("D[1]=",D[1]) Mat=[] i=0 while i<4: lin=[] j=0 while j<4: lin=lin+[0] j=j+1 Mat=Mat+[lin] i=i+1 print("mat=",Mat) print("mat[1]=",Mat[1]) mat[1][1]=2 print("mat=",Mat) #--------- main()