framework::config Namespace Reference

python execution and parameter extraction More...

Classes
class	Parameters
	Class encapsulating parameters for configuring a processor. More...

Functions
Parameters	run (const std::string &root_object, const std::string &pythonScript, char *args[], int nargs)
	run the python script and extract the parameters
static std::string	getPyString (PyObject *pyObj)
	Turn the input python string object into a std::string.
std::string	repr (PyObject *obj)
	Get a C++ string representation of the input python object.
PyObject *	extractDictionary (PyObject *obj)
	extract the dictionary of attributes from the input python object
static Parameters	getMembers (PyObject *object)
	Extract members from a python object.

Detailed Description

python execution and parameter extraction

this namespace is focused on holding the necessary functions to run and extract the configuration parameters from a python script. The documentation here is focused on the C++-side of the configuration - i.e. the translation of Python objects into their C++ counterparts.

Function Documentation

extractDictionary()

PyObject * framework::config::extractDictionary

(

PyObject *

obj

)

extract the dictionary of attributes from the input python object

This is separated into its own function to isolate the code that depends on the python version. Since memory-saving measures were integrated into Python between 3.6.9 and 3.10.6, we need to alter how we were using the C API to access an objects dict attribute. We are now using a "hidden" Python C API function which has only been added to the public C API documentation in Python 3.11. It has been manually tested for the two different Python versions we use by running the tests (some of which test the ConfigurePython) and running a basic simulation.

Exceptions

Exception

if object does not have a dict and isn't a dict

Parameters

obj	pointer to python object to extract from

Returns

pointer to python dictionary for its members

This was developed for Python3.10 when upgrading to Ubuntu 22.04 in the development container image. A lot of memory-saving measures were taken which means we have to explicitly ask Python to construct the dict object for us so that it knows to "waste" the memory on it.

https://docs.python.org/3/c-api/object.html

We use _PyObject_GetDictPtr because that will not set an error if the dict does not exist.

Definition at line 99 of file Python.cxx.

                                           {
  PyObject** p_dictionary{_PyObject_GetDictPtr(obj)};
  if (p_dictionary == NULL) {
    if (PyDict_Check(obj)) {
      return obj;
    } else {
      EXCEPTION_RAISE("ObjFail",
                      "Python Object '" + repr(obj) +
                          "' does not have __dict__ member and is not a dict.");
    }
  }
  return *p_dictionary;
}

References repr().

Referenced by getMembers().

getMembers()

static Parameters framework::config::getMembers ( PyObject * object )

static

Extract members from a python object.

Iterates through the object's dictionary and translates the objects inside of it into the type-specified C++ equivalents, then puts these objects into an instance of the Parameters class.

This function is recursive. If a non-base type is encountered, we pass it back along to this function to translate it's own dictionary.

We rely completely on python being awesome. For all higher level class objects, python keeps track of all of its member variables in the member dictionary __dict__.

No Py_DECREF calls are made because all of the members of an object are borrowed references, meaning that when we destory that object, it handles the other members. We destroy the one Python object owning all of these references at the end of this function.

Note

Not sure if this is not leaking memory, kinda just trusting the Python / C API docs on this one.

Empty lists are NOT read in because there is no way for us to know what type should be inside the list. This means list parameters that can be empty need to put in a default empty list value: {}.

This recursive extraction method is able to handle the following cases.

• User-defined classes (via the __dict__ member) are extracted to Parameters
• one-dimensional lists whose entries all have the same type are extracted to std::vector of the type of the first entry in the list
• dict objects are extracted to Parameters
• Python str are extracted to std::string
• Python int are extracted to C++ int
• Python bool are extracted to C++ bool
• Python float are extracted to C++ double

Known design flaws include

• No support for nested Python lists
• Annoying band-aid solution for empty Python lists

Parameters

[in]

object

Python object to get members from

Returns

Mapping between member name and value.

Definition at line 169 of file Python.cxx.

                                               {
  PyObject* dictionary{extractDictionary(object)};
  PyObject *key(0), *value(0);
  Py_ssize_t pos = 0;
 
  Parameters params;
 
  while (PyDict_Next(dictionary, &pos, &key, &value)) {
    std::string skey{getPyString(key)};
 
    if (PyLong_Check(value)) {
      if (PyBool_Check(value)) {
        params.add(skey, bool(PyLong_AsLong(value)));
      } else {
        params.add(skey, int(PyLong_AsLong(value)));
      }
    } else if (PyFloat_Check(value)) {
      params.add(skey, PyFloat_AsDouble(value));
    } else if (PyUnicode_Check(value)) {
      params.add(skey, getPyString(value));
    } else if (PyList_Check(value)) {
      // assume everything is same value as first value
      if (PyList_Size(value) > 0) {
        auto vec0{PyList_GetItem(value, 0)};
 
        if (PyLong_Check(vec0)) {
          std::vector<int> vals;
 
          for (auto j{0}; j < PyList_Size(value); j++)
            vals.push_back(PyLong_AsLong(PyList_GetItem(value, j)));
 
          params.add(skey, vals);
 
        } else if (PyFloat_Check(vec0)) {
          std::vector<double> vals;
 
          for (auto j{0}; j < PyList_Size(value); j++)
            vals.push_back(PyFloat_AsDouble(PyList_GetItem(value, j)));
 
          params.add(skey, vals);
 
        } else if (PyUnicode_Check(vec0)) {
          std::vector<std::string> vals;
          for (Py_ssize_t j = 0; j < PyList_Size(value); j++) {
            PyObject* elem = PyList_GetItem(value, j);
            vals.push_back(getPyString(elem));
          }
 
          params.add(skey, vals);
        } else if (PyList_Check(vec0)) {
          // a list in a list ??? oof-dah
          if (PyList_Size(vec0) > 0) {
            auto vecvec0{PyList_GetItem(vec0, 0)};
            if (PyLong_Check(vecvec0)) {
              std::vector<std::vector<int>> vals;
              for (auto j{0}; j < PyList_Size(value); j++) {
                auto subvec{PyList_GetItem(value, j)};
                std::vector<int> subvals;
                for (auto k{0}; k < PyList_Size(subvec); k++) {
                  subvals.push_back(PyLong_AsLong(PyList_GetItem(subvec, k)));
                }
                vals.push_back(subvals);
              }
              params.add(skey, vals);
            } else if (PyFloat_Check(vecvec0)) {
              std::vector<std::vector<double>> vals;
              for (auto j{0}; j < PyList_Size(value); j++) {
                auto subvec{PyList_GetItem(value, j)};
                std::vector<double> subvals;
                for (auto k{0}; k < PyList_Size(subvec); k++) {
                  subvals.push_back(
                      PyFloat_AsDouble(PyList_GetItem(subvec, k)));
                }
                vals.push_back(subvals);
              }
              params.add(skey, vals);
            } else if (PyUnicode_Check(vecvec0)) {
              std::vector<std::vector<std::string>> vals;
              for (auto j{0}; j < PyList_Size(value); j++) {
                auto subvec{PyList_GetItem(value, j)};
                std::vector<std::string> subvals;
                for (auto k{0}; k < PyList_Size(subvec); k++) {
                  subvals.push_back(getPyString(PyList_GetItem(subvec, k)));
                }
                vals.push_back(subvals);
              }
              params.add(skey, vals);
            } else if (PyList_Check(vecvec0)) {
              EXCEPTION_RAISE("BadConf",
                              "A python list with dimension greater than 2 is "
                              "not supported.");
            } else {
              // RECURSION zoinks!
              std::vector<std::vector<framework::config::Parameters>> vals;
              for (auto j{0}; j < PyList_Size(value); j++) {
                auto subvec{PyList_GetItem(value, j)};
                std::vector<framework::config::Parameters> subvals;
                for (auto k{0}; k < PyList_Size(subvec); k++) {
                  subvals.emplace_back(getMembers(PyList_GetItem(subvec, k)));
                }
                vals.push_back(subvals);
              }
              params.add(skey, vals);
            }
          }  // non-zero size
        } else {
          // RECURSION zoinks!
          // If the objects stored in the list doesn't
          // satisfy any of the above conditions, just
          // create a vector of parameters objects
          std::vector<framework::config::Parameters> vals;
          for (auto j{0}; j < PyList_Size(value); ++j) {
            auto elem{PyList_GetItem(value, j)};
            vals.emplace_back(getMembers(elem));
          }
          params.add(skey, vals);
        }  // type of object in python list
      }  // python list has non-zero size
    } else {
      // object got here, so we assume
      // it is a higher level object
      //(same logic as last option for a list)
 
      // RECURSION zoinks!
      params.add(skey, getMembers(value));
    }  // python object type
  }  // loop through python dictionary
 
  return params;
}

References framework::config::Parameters::add(), extractDictionary(), getMembers(), and getPyString().

Referenced by getMembers(), and run().

getPyString()

static std::string framework::config::getPyString ( PyObject * pyObj )

static

Turn the input python string object into a std::string.

Helpful to condense down the multi-line nature of the python3 code.

Parameters

[in]

pyObj

python object assumed to be a string python object

Returns

the value stored in it

Definition at line 58 of file Python.cxx.

                                              {
  std::string retval;
  PyObject* py_str = PyUnicode_AsEncodedString(pyObj, "utf-8", "Error ~");
  retval = PyBytes_AS_STRING(py_str);
  Py_XDECREF(py_str);
  return retval;
}

Referenced by getMembers(), and repr().

repr()

std::string framework::config::repr

(

PyObject *

obj

)

Get a C++ string representation of the input python object.

This is replicating the repr(obj) syntax of Python.

Parameters

[in]

obj

python object to get repr for

Returns

std::string form of repr

Definition at line 74 of file Python.cxx.

                              {
  PyObject* py_repr = PyObject_Repr(obj);
  if (py_repr == nullptr) return "";
  std::string str = getPyString(py_repr);
  Py_XDECREF(py_repr);
  return str;
}

References getPyString().

Referenced by extractDictionary().

run()

Parameters framework::config::run	(	const std::string &	root_object,
		const std::string &	pythonScript,
		char *	args[],
		int	nargs )

run the python script and extract the parameters

This method contains all the parsing and execution of the python script.

Exceptions

Exception	if the python script does not exit properly
Exception	if any necessary components of the python configuration are missing. e.g. The Process class or the different members of the lastProcess object.

The basic premise of this function is to execute the python configuration script. Then, after the script has been executed, all of the parameters for the Process are gathered from python. The fact that the script has been executed means that the user can get up to a whole lot of shenanigans that can help them make their work more efficient.

Parameters

[in]	full	pythonic path to the object to kickoff extraction
[in]	pythonScript	Filename location of the python script.
[in]	args	Commandline arguments to be passed to the python script.
[in]	nargs	Number of commandline arguments, assumed to be >= 0

Definition at line 300 of file Python.cxx.

                                        {
  // assumes that nargs >= 0
  //  this is true always because we error out if no python script has been
  //  found
 
  // load a handle to the config file into memory (and check that it exists)
  std::unique_ptr<FILE, int (*)(FILE*)> fp{fopen(pythonScript.c_str(), "r"),
                                           &fclose};
  if (fp.get() == NULL) {
    EXCEPTION_RAISE("ConfigDNE",
                    "Passed config script '" + pythonScript +
                        "' is not accessible.\n"
                        "    Did you make a typo in the path to the script?\n"
                        "    Are you referencing a directory that is not "
                        "mounted to the container?");
  }
 
  // python needs the argument list as if you are on the command line
  //  targs = [ script , arg0 , arg1 , ... ] ==> len(targs) = nargs+1
  // the updated Python3.12 (DEV_IMAGE_MAJOR == 5) C API looks to have
  // more helper functions to avoid having to do this ourselves, but
  // I think sharing the same targs between the different Python versions
  // makes the code cleaner
  wchar_t** targs = new wchar_t*[nargs + 1];
  targs[0] = Py_DecodeLocale(pythonScript.c_str(), NULL);
  for (int i = 0; i < nargs; i++) targs[i + 1] = Py_DecodeLocale(args[i], NULL);
 
#if DEV_IMAGE_MAJOR < 5
  // name our program after the script that is being run
  Py_SetProgramName(targs[0]);
 
  // start up python interpreter
  Py_Initialize();
 
  // The third argument to PySys_SetArgvEx tells python to import
  // the args and add the directory of the first argument to
  // the PYTHONPATH
  // This way, the command to import the module_ just needs to be
  // the name of the python script
  PySys_SetArgvEx(nargs + 1, targs, 1);
#else
  PyStatus status;
  PyConfig config;
  PyConfig_InitPythonConfig(&config);
  // we do not want python to parse our args (we are already doing that)
  config.parse_argv = 0;
  // note to future developers: the embedding docs encourage users to
  // set config.isolated = 1 in order to more securely embed python.
  // we do /not/ want to do this because we want to inherit the
  // external environment of python
 
  // copy over program name
  status = PyConfig_SetString(&config, &config.program_name, targs[0]);
  if (PyStatus_Exception(status)) {
    PyConfig_Clear(&config);
    Py_ExitStatusException(status);
    EXCEPTION_RAISE("PyConfigInit",
                    "Unable to set the program name in the python config.");
  }
  // copy over updated argument vector
  status = PyConfig_SetArgv(&config, nargs + 1, targs);
  if (PyStatus_Exception(status)) {
    PyConfig_Clear(&config);
    Py_ExitStatusException(status);
    EXCEPTION_RAISE("PyConfigInit",
                    "Unable to set argv for the python config.");
  }
  // read and solidify the configuration
  status = PyConfig_Read(&config);
  if (PyStatus_Exception(status)) {
    PyConfig_Clear(&config);
    Py_ExitStatusException(status);
    EXCEPTION_RAISE("PyConfigInit", "Unable to read the python config.");
  }
  // initialize the python interpreter with our deduced configuration
  status = Py_InitializeFromConfig(&config);
  if (PyStatus_Exception(status)) {
    PyConfig_Clear(&config);
    Py_ExitStatusException(status);
    Py_FinalizeEx();
    EXCEPTION_RAISE("PyConfigInit",
                    "Unable to initilize the python interpreter.");
  }
  // don't need config anymore now that the initialization is done
  PyConfig_Clear(&config);
#endif
 
  if (PyRun_SimpleFile(fp.get(), pythonScript.c_str()) != 0) {
    // running the script executed with an error
    PyErr_Print();
    Py_FinalizeEx();
    EXCEPTION_RAISE("Python", "Execution of python script failed.");
  }
 
  // script has been run so we can
  // free up arguments to python script
  for (int i = 0; i < nargs + 1; i++) PyMem_RawFree(targs[i]);
  delete[] targs;
 
  // running a python script effectively imports the script into the top-level
  // code environment called '__main__'
  //  we "import" this module_ which is already imported to get a handle
  //  on the necessary objects
  PyObject* py_root_obj = PyImport_ImportModule("__main__");
  if (!py_root_obj) {
    PyErr_Print();
    Py_FinalizeEx();
    EXCEPTION_RAISE("Python",
                    "I don't know what happened. This should never happen.");
  }
 
  // descend the hierarchy of modules that hold the root_object
  // manually expanding the '.' allows us to handle all of the different
  // cases of how the configuration Python class could have been imported
  // and constructed
  std::string attr;
  std::stringstream root_obj_ss{root_object};
  while (std::getline(root_obj_ss, attr, '.')) {
    PyObject* one_level_down =
        PyObject_GetAttrString(py_root_obj, attr.c_str());
    if (one_level_down == 0) {
      Py_FinalizeEx();
      EXCEPTION_RAISE("Python", "Unable to find python object '" + attr + "'.");
    }
    Py_DECREF(py_root_obj);  // don't need previous python object anymore
    py_root_obj = one_level_down;
  }
 
  // now py_root_obj should hold the root configuration object
  if (py_root_obj == Py_None) {
    // root config object left undefined
    Py_FinalizeEx();
    EXCEPTION_RAISE("Python",
                    "Root configuration object " + root_object +
                        " not defined. This object is required to run.");
  }
 
  // okay, now we have fully imported the script and gotten the handle
  // to the root configuration object defined in the script.
  // We can now look at this object and recursively get all of our parameters
  // out of it.
 
  Parameters configuration(getMembers(py_root_obj));
 
  // all done with python nonsense
  // delete one parent python object
  // MEMORY still not sure if this is enough, but not super worried about it
  //  because this only happens once per run
  Py_DECREF(py_root_obj);
  // close up python interpreter
  if (Py_FinalizeEx() < 0) {
    PyErr_Print();
    EXCEPTION_RAISE("Python",
                    "I wasn't able to close up the python interpreter!");
  }
 
  return configuration;
}

References getMembers().