Python in a Nutshell

Name

outer

Synopsis

                        u.outer(a,b)

Returns an array r whose shape tuple is a .shape+ b .shape. For each tuple ta indexing a and tb indexing b, a [ ta ], operated (with the function or operator underlying u) with b [ tb ], is put in r [ ta + tb ] (the + here indicates tuple concatenation). The overall operation is known in mathematics as the outer product when u is multiply. For example:

a = Numeric.arange(3, 5)
b = Numeric.arange(1, 6)
c = Numeric.multiply.outer(a, b)
print a.shape, b.shape, c.shape # prints: (2,) (5,) (2,5)
print c                         # prints: [[3 6 9 12 15]
                                #          [4 8 12 16 20]]

c .shape is (2,5), the concatenation of the shape tuples of operands a and b. Each i row of c is the whole of b multiplied by the corresponding i element of a.