If y is a theano variable, y.shape will be a theano variable. so it is normal that
print y.shape
return:
Shape.0
If you want to evaluate the expression y.shape, you can do:
y.shape.eval()
if y.shape do not input to compute itself(it depend only on shared variable and constant). Otherwise, if y depend on the x Theano variable you can pass the inputs value like this:
y.shape.eval(x=numpy.random.rand(...))
this is the same thing for the sum. Theano graph are symbolic variable that do not do computation until you compile it with theano.function or call eval() on them.
EDIT: Per the docs, the syntax in newer versions of theano is
y.shape.eval({x: numpy.random.rand(...)})