Example for gh-3040. Allow numpy.exp(theano_var) to build a graph.

theano/tensor/tests/test_var.py

+import numpy as np
+
+import theano
+import theano.tensor as tt
+import theano.tests.unittest_tools as utt
+
+
+def test_numpy_method():
+    # This type of code is used frequently by PyMC3 users
+    x = tt.dmatrix('x')
+    data = np.random.rand(5, 5)
+    for fct in [np.exp]:
+        print fct
+        y = fct(x)
+        f = theano.function([x], y)
+        utt.assert_allclose(f(data), fct(data))

theano/tensor/var.py

@@ -354,6 +354,10 @@ class _tensor_py_operators:
     def diagonal(self, offset=0, axis1=0, axis2=1):
         return theano.tensor.basic.diagonal(self, offset, axis1, axis2)
 
+    # Elemwise
+    def exp(self):
+        return theano.tensor.exp(self)
+
     # CASTING
     def astype(self, dtype):
         return theano.tensor.cast(self, dtype)