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I don't know how to convert a matrix of 10x10 into four matrices of 5x5, for example:

[[10, 11, 12, 13, 14, 15, 16, 17, 18, 19], # matrix 10x10
 [20, 21, 22, 23, 24, 25, 26, 27, 28, 29],
 [30, 31, 32, 33, 34, 35, 36, 37, 38, 39],
 [40, 41, 42, 43, 44, 45, 46, 47, 48, 49],
 [50, 51, 52, 53, 54, 55, 56, 57, 58, 59],
 [60, 61, 62, 63, 64, 65, 66, 67, 68, 69],
 [10, 11, 12, 13, 14, 15, 16, 17, 18, 19],
 [20, 21, 22, 23, 24, 25, 26, 27, 28, 29],
 [30, 31, 32, 33, 34, 35, 36, 37, 38, 39],
 [40, 41, 42, 43, 44, 45, 46, 47, 48, 49]]

I need to convert into this:

[[10, 11, 12, 13, 14] # 4 like this with the other numbers too
 [20, 21, 22, 23, 24] 
 [30, 31, 32, 33, 34]
 [40, 41, 42, 43, 44]
 [50, 51, 52, 53, 54]]
Igal
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  • possible duplicate of [how to split matrix into 4 quadrants in python using numpy](http://stackoverflow.com/questions/25855180/how-to-split-matrix-into-4-quadrants-in-python-using-numpy) and [how to split a matrix into 4 blocks using numpy](http://stackoverflow.com/questions/11105375/how-to-split-a-matrix-into-4-blocks-using-numpy) – fredtantini Oct 29 '14 at 15:36

1 Answers1

2

You can use slicing and a list comprehension:

>>> matrix = \
... [[10, 11, 12, 13, 14, 15, 16, 17, 18, 19],
...  [20, 21, 22, 23, 24, 25, 26, 27, 28, 29],
...  [30, 31, 32, 33, 34, 35, 36, 37, 38, 39],
...  [40, 41, 42, 43, 44, 45, 46, 47, 48, 49],
...  [50, 51, 52, 53, 54, 55, 56, 57, 58, 59],
...  [60, 61, 62, 63, 64, 65, 66, 67, 68, 69],
...  [10, 11, 12, 13, 14, 15, 16, 17, 18, 19],
...  [20, 21, 22, 23, 24, 25, 26, 27, 28, 29],
...  [30, 31, 32, 33, 34, 35, 36, 37, 38, 39],
...  [40, 41, 42, 43, 44, 45, 46, 47, 48, 49]]
>>> from pprint import pprint
>>> pprint([x[:5] for x in matrix[:5]])
[[10, 11, 12, 13, 14],
 [20, 21, 22, 23, 24],
 [30, 31, 32, 33, 34],
 [40, 41, 42, 43, 44],
 [50, 51, 52, 53, 54]]
>>>

sequence[:5] gets the first five items in sequence. So, matrix[:5] gets the first five sublists in matrix and x[:5] gets the first five items in each of those sublists. pprint.pprint is only used to format the output.

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