The shape of a matrix is the tuple of its dimensions. The shape of an n × m matrix is the tuple (n, m). It can be obtained by the shape function:

M = identity(3)
shape(M) # (3, 3)

For a vector, the shape is a singleton containing the length of that vector:

v = array([1., 2., 1., 4.])
shape(v) # (4,) <- singleton (1-tuple)

An alternative is to use the array attribute shape, which gives  the same result:

M = array([[1.,2.]])
shape(M) # (1,2)
M.shape # (1,2)

However, the advantage of using  shape as a function is that this function may be used on scalars and lists as well. This may come in handy when code is supposed to work with both scalars and arrays:

shape(1.) # ()
shape([1,2]) # (2...