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# problem with two-dimensional list/array

 P: 20 hi, i've created a 2D list(ie: A=[]). i choose some of element from the list(ie: A,A,A) and do simple add operations. Then i created another empty 2D list to store the result. but i wanted the result to be stored at a specific index (ie: at B=,B,B). but i get an error."Error - list index out of range " here is my code...can anyone spot my mistake... Expand|Select|Wrap|Line Numbers A=[]         for i in range(3):             A.append([]) A=(1,3,4,5) A=(2,4,6,5) A=(3,6,7,4)   B=[]       for j in range(3):              B.append([])              for i in range(3):                  B[i][i]=2+A[i][i]     Sep 2 '10 #1

Your indentation is wrong, but I suspect it is a copy/paste problem.

You did not initialize list B properly.
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1. A=[]
2. for i in range(3):
3.     A.append([])
4. A=(1,3,4,5)
5. A=(2,4,6,5)
6. A=(3,6,7,4)
7.
8. B=[[None for i in range(4)] for j in range(3)]
9.
10. for i in range(3):
11.     B[i][i]=2+A[i][i]
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1. >>> B
2. [[3, None, None, None], [None, 6, None, None], [None, None, 9, None]]
3. >>> 