Task

Build an   identity matrix   of a size known at run-time.



An identity matrix is a square matrix of size n × n,

where the diagonal elements are all 1s (ones),

and all the other elements are all 0s (zeroes).







I

n


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1


0


0


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0




0


1


0


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0




0


0


1


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0


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{\displaystyle I_{n}={\begin{bmatrix}1&0&0&\cdots &0\\0&1&0&\cdots &0\\0&0&1&\cdots &0\\\vdots &\vdots &\vdots &\ddots &\vdots \\0&0&0&\cdots &1\\\end{bmatrix}}}





Related tasks

   Spiral matrix
   Zig-zag matrix 
   Ulam_spiral_(for_primes)


def identity(size):
    matrix = [[0]*size for i in range(size)]
    #matrix = [[0] * size] * size    #Has a flaw. See http://stackoverflow.com/questions/240178/unexpected-feature-in-a-python-list-of-lists
 
    for i in range(size):
        matrix[i][i] = 1
 
    for rows in matrix:
        for elements in rows:
            print elements,
        print ""