update to docs

Signed-off-by: Alex McCaskey <mccaskeyaj@ornl.gov>

docs/source/extensions.rst

@@ -673,7 +673,7 @@ To use this Observable, ensure you have Psi4 installed under the same
    $ git clone https://github.com/psi4/psi4 && cd psi4 && mkdir build && cd build
    $ cmake .. -DPYTHON_EXECUTABLE=$(which python3) -DCMAKE_INSTALL_PREFIX=$(python3 -m site --user-site)/psi4
    $ make -j8 install
-   $ export PYTHONPATH=$(python3 -m site --user-site)/psi4:$PYTHONPATH
+   $ export PYTHONPATH=$(python3 -m site --user-site)/psi4/lib:$PYTHONPATH
 
 This observable type takes an dictionary of options describing the
 molecular geometry (key ``geometry``), the basis set (key ``basis``),

python/examples/nah_vqe_ucc1.py

 import xacc
-import sys
-import numpy as np
 
 # Get access to the desired QPU and
 # allocate some qubits to run on

python/py_observable.cpp

@@ -114,6 +114,9 @@ void bind_observable(py::module &m) {
             t = xacc::getContributedService<Observable>(type, false);
           }
 
+          if (!t) {
+              xacc::error("Invalid Observable type name " + type + ", can't find in service registry.");
+          }
           HeterogeneousMap m;
           for (auto &item : options) {
             PyHeterogeneousMap2HeterogeneousMap vis(m, item.first);
@@ -122,4 +125,21 @@ void bind_observable(py::module &m) {
           t->fromOptions(m);
           return t;
         });
+        
+      m.def("getObservable",
+        [](const std::string &type) -> std::shared_ptr<Observable> {
+          std::shared_ptr<Observable> t;
+          if (xacc::hasService<Observable>(type)) {
+            t = xacc::getService<Observable>(type, false);
+          } else if (xacc::hasContributedService<Observable>(type)) {
+            t = xacc::getContributedService<Observable>(type, false);
+          }
+
+          if (!t) {
+              xacc::error("Invalid Observable type name " + type + ", can't find in service registry.");
+          }
+          HeterogeneousMap m;
+          t->fromOptions(m);
+          return t;
+        });
 }
\ No newline at end of file

python/xacc-py.cpp

@@ -115,6 +115,18 @@ PYBIND11_MODULE(_pyxacc, m) {
           accd->setDecorated(acc);
           return accd;
         });
+  m.def("getAcceleratorDecorator",
+        [](const std::string name, std::shared_ptr<Accelerator> acc, const PyHeterogeneousMap& options) {
+          auto accd = xacc::getService<AcceleratorDecorator>(name);
+          accd->setDecorated(acc);
+          HeterogeneousMap m;
+          for (auto &item : options) {
+            PyHeterogeneousMap2HeterogeneousMap vis(m, item.first);
+            mpark::visit(vis, item.second);
+          }
+          accd->initialize(m);
+          return accd;
+        });
   m.def("asComposite", &xacc::ir::asComposite, "");
   m.def("asInstruction", &xacc::ir::asInstruction, "");
   m.def(

python/xacc.py

@@ -290,7 +290,8 @@ class PyServiceRegistry(object):
 
     def initialize(self):
         serviceList = ['decorator_algorithm_service', 'benchmark_algorithm',
-                       'hamiltonian_generator', 'ansatz_generator', 'accelerator', 'irtransformation', 'observable']
+                       'hamiltonian_generator', 'ansatz_generator', 'accelerator',
+                       'irtransformation', 'observable']
         xaccLocation = os.path.dirname(os.path.realpath(__file__))
         self.pluginDir = xaccLocation + '/py-plugins'
         if not os.path.exists(self.pluginDir):