Added traversing capability to the Results object, added a new Exception class...

Added traversing capability to the Results object, added a new Exception class that is raised when a certain valid metainfo was not outputted by the parser.

common/python/nomadcore/local_backend.py

 from __future__ import print_function
 from future import standard_library
 standard_library.install_aliases()
+from enum import Enum
 from operator import itemgetter
 from builtins import range
 from builtins import object
@@ -11,7 +12,23 @@ from collections import defaultdict
 logger = logging.getLogger(__name__)
 
 
-#===============================================================================
+class ParserEvent(Enum):
+    """Enumerations for the different parser events when traversing the
+    results.
+    """
+    open_section = 1
+    close_section = 2
+    add_value = 3
+    add_array_value = 4
+
+
+class ParserKeyError(Exception):
+    """A custom exception for all cases where a certain metainfo can not be
+    found in the results.
+    """
+    pass
+
+
 class DummyFile(object):
     """Mimics a file object by defininf a write interface, but actually does
     not write anything. This allows one to used this object in functions which
@@ -22,7 +39,6 @@ class DummyFile(object):
         pass
 
 
-#===============================================================================
 class LocalBackend(object):
     """A backend that outputs results into a regular python dictionary. This is
     useful if you wan't to run the parser with python only.
@@ -266,14 +282,14 @@ class Results(object):
             sectionmanager = datamanager.superSectionManager
             open_sections = sectionmanager.openSections
             result = []
-            for section in open_sections.values():
+            for section in open_sections:
                 data = section[metaname]
                 if data is not None:
                     result.append(data)
             if len(result) == 1:
                 return result[0]
             elif len(result) == 0:
-                raise LookupError("Could not find a parsing result for '{}'. The parser did not output this value.".format(metaname))
+                raise ParserKeyError("Could not find a parsing result for '{}'. The parser did not output this value.".format(metaname))
             else:
                 return np.array(result)
 
@@ -286,6 +302,33 @@ class Results(object):
         if metainfo is None:
             raise LookupError("The metainfo name '{}' does not exist in the metainfo environment. Check for typos or try updating the metainfo git package.".format(metaname))
 
+    def traverse(self):
+        """A generator function for traversing the data in the parser results.
+
+        This generator returns a tuple of three item: the metainfo name, the
+        event type, and the event value.
+        """
+        root = self._sectionmanagers["section_run"]
+        roots = {"section_run": []}
+        for section in root.openSections:
+            roots["section_run"].append(section)
+        for x in self.traverse_recursive(roots):
+            yield x
+
+    def traverse_recursive(self, section_map):
+        """A generator function for traversing the data in the parser results.
+        """
+        for name, sections in section_map.items():
+            for section in sections:
+                yield (name, ParserEvent.open_section, None)
+                for name, value in section.simpleValues.items():
+                    yield (name, ParserEvent.add_value, value)
+                for name, value in section.arrayValues.items():
+                    yield (name, ParserEvent.add_array_value, value)
+                for x in self.traverse_recursive(section.subSectionValues):
+                    yield x
+                yield (name, ParserEvent.close_section, None)
+
     def print_summary(self):
         """Return a string representing the data contained in the results. This
         is a summary that can be used for debugging.
@@ -378,8 +421,13 @@ class Section(object):
         if res is not None:
             return res
         res = self.subSectionValues.get(metaName, None)
+        if res is not None:
             return res
 
+        raise ParserKeyError(
+            "The metainfo '{}' could not be found in the section '{}'"
+            .format(metaName, self.name))
+
     def addValue(self, metaInfo, value):
         if self.backend.store:
             vals = self.simpleValues.get(metaInfo.name, None)
@@ -420,11 +468,11 @@ class Section(object):
 class SectionManager(object):
     """Manages the sections for the given metainfo.
     """
-    def __init__(self, metaInfo, parentSectionNames, lastSectionGIndex=-1, openSections={}):
+    def __init__(self, metaInfo, parentSectionNames, lastSectionGIndex=-1):
         self.metaInfo = metaInfo
         self.parentSectionNames = parentSectionNames
         self.lastSectionGIndex = lastSectionGIndex
-        self.openSections = dict(openSections)
+        self.openSections = []
 
     def openSection(self, backend):
         newGIndex = self.lastSectionGIndex + 1
@@ -455,7 +503,10 @@ class SectionManager(object):
         if not parent_found and len(self.parentSectionNames) != 0:
             raise LookupError("Could not open section '{}' because none of it's parent sections '{}' could not be found".format(self.metaInfo.name, self.parentSectionNames))
 
-        self.openSections[gIndex] = Section(gIndex, references, parents, self.metaInfo.name, backend)
+        new_section = Section(gIndex, references, parents, self.metaInfo.name, backend)
+        self.openSections.append(new_section)
+        if parent_found:
+            parents[0].addSubsection(self.metaInfo, new_section)
 
     def closeSection(self, backend, gIndex):
         pass