add def for getting values out of the material data

src/materials.py

@@ -103,6 +103,9 @@ def search_keys(data, keys):
   from json import loads
 
   def find_values(key, json_repr):
+    """\
+    Find values inside json string
+    """
     results = []
     def _decode_dict(a_dict):
       try:
@@ -146,6 +149,19 @@ def print_quantity(quantity, prespaces=0):
     print(prespaces*' ' + '%s' % quantity)
 
 
+def get_value(data, element):
+  """\
+  Get value of nested dictionary.
+  If element is itself a list of length one, the element of the list is returned
+  """
+  keys = element.split('/')
+  for key in keys:
+    data = data.get(key)
+  if data and len(data) == 1:
+    data = next(iter(data.values()))
+  return data
+
+
 def main():
   """\
   Main function
@@ -209,25 +225,20 @@ def main():
       if args.debug:
         print("data:")
         print_material(data)
+      mat_index = {
+        "rho": "Mechanical Properties/rho",
+        "E": "Mechanical Properties/E",
+        "R_p": "Mechanical Properties/Yield strength",
+        "R_m": "Mechanical Properties/R_m"
+      }
       for element in args.const_collection:  # iter the way it is been entered as args
-        if element == "rho":
-          print_quantity(data['Mechanical Properties']['rho'])
-        elif element == "E":
-          print_quantity(data['Mechanical Properties']['E'])
-        elif element == "R_p":
-          if len(data['Mechanical Properties']['Yield strength']) == 1:
-            print_quantity(next(iter(data['Mechanical Properties']['Yield strength'].values())))
-          else:
-            print_quantity(data['Mechanical Properties']['Yield strength'])
-        elif element == "R_m":
-          print_quantity(data['Mechanical Properties']['R_m'])
+        print_quantity(get_value(data, mat_index[element]))
 
     elif args.search:
       search_list = [element for element in args.search.split(',')]
-      if args.debug:
-        print("search_list: " + str(search_list))
       data = read_material(args.materialname)
       if args.debug:
+        print("search_list: " + str(search_list))
         print("data: " + data)
       data_dict = search_keys(data, keys=search_list)
       print_dict(data_dict)