import numpy as np
import theano.tensor as T
from theano import function

# basic
x = T.dscalar('x')
y = T.dscalar('y')
z = x + y
f = function([x,y],z)

print(f(2,3))

# to pretty-print the function
from theano import pp
print(pp(z))

# how about matrix
x = T.dmatrix('x')
y = T.dmatrix('y')
z = x + y
f = function([x,y],z)
print(f(np.arange(12).reshape((3,4)),10*np.ones((3,4))))

result:

5.0
(x + y)
[[ 10.  11.  12.  13.]
 [ 14.  15.  16.  17.]
 [ 18.  19.  20.  21.]]