identity_matx.py

# Given a list of lists representing a n * n matrix as input,
# The procedure that returns True if the input is an identity matrix
# and False otherwise.

# An IDENTITY matrix is a square matrix in which all the elements
# on the principal/main diagonal are 1 and all the elements outside
# the principal diagonal are 0.
# (A square matrix is a matrix in which the number of rows
# is equal to the number of columns)

def is_identity_matrix(test):
    if not test : return False
    le = len(test[0])
    for i,x in enumerate(test):
        if len(x) == le:
            if any(y!=1 if j==i else y!=0 for j,y in enumerate(x)):
                return False
        else:
            return False
    return True if len(test) == le else False



# Test Cases:

matrix1 = [[1,0,0,0],
           [0,1,0,0],
           [0,0,1,0],
           [0,0,0,1]]
print is_identity_matrix(matrix1)
#>>>True

matrix2 = [[1,0,0],
           [0,1,0],
           [0,0,0]]

print is_identity_matrix(matrix2)
#>>>False

matrix3 = [[2,0,0],
           [0,2,0],
           [0,0,2]]

print is_identity_matrix(matrix3)
#>>>False

matrix4 = [[1,0,0,0],
           [0,1,1,0],
           [0,0,0,1]]

print is_identity_matrix(matrix4)
#>>>False

matrix5 = [[1,0,0,0,0,0,0,0,0]]

print is_identity_matrix(matrix5)
#>>>False

matrix6 = [[1,0,0,0],
           [0,1,0,1],
           [0,0,1,0],
           [0,0,0,1]]

print is_identity_matrix(matrix6)
#>>>False

matrix7 = [[1, -1, 1],
           [0, 1, 0],
           [0, 0, 1]]
print is_identity_matrix(matrix7)
#>>>False