added a new error type to deal with attempting to get / set a command feature data type

2 files changed, 12 insertions, 4 deletions

diff --git a/pymba/feature.py b/pymba/feature.py
index 7ac403d..9156bad 100644
--- a/pymba/feature.py
+++ b/pymba/feature.py
@@ -80,6 +80,11 @@ class Feature:
             'range': 2,
         }
 
+        # doesn't make sense to get / set a command data type
+        if data_type == _FEATURE_DATA_COMMAND:
+            raise VimbaException(VimbaException.ERR_COMMAND_MUST_BE_CALLED)
+
+        # some data types aren't implemented
         try:
             return access_funcs[data_type][access_indices[func_type]]
         except IndexError:
diff --git a/pymba/vimba_exception.py b/pymba/vimba_exception.py
index 22f03c2..992e299 100644
--- a/pymba/vimba_exception.py
+++ b/pymba/vimba_exception.py
@@ -24,11 +24,13 @@ class VimbaException(Exception):
         ERR_FEATURE_NOT_SUPPORTED,
         ERR_PARTIAL_REGISTER_ACCESS,
 
-        # -50 to -56
+        # -50 to -53
+        ERR_UNDEFINED_ERROR_CODE,
         ERR_FRAME_BUFFER_MEMORY,
         ERR_NOT_IMPLEMENTED_IN_PYMBA,
-        ERR_UNDEFINED_ERROR_CODE,
-    ) = tuple(range(0, -20, -1)) + tuple(range(-50, -53, -1))
+        ERR_COMMAND_MUST_BE_CALLED,
+    ) = tuple(range(0, -20, -1)) + \
+        tuple(range(-50, -54, -1))
 
     ERRORS = {
         # Vimba C API specific errors
@@ -54,9 +56,10 @@ class VimbaException(Exception):
         ERR_PARTIAL_REGISTER_ACCESS: 'A multiple registers read or write was partially completed.',
 
         # Custom errors
+        ERR_UNDEFINED_ERROR_CODE: 'Undefined error code',
         ERR_FRAME_BUFFER_MEMORY: 'Not enough memory to assign frame buffer.',
         ERR_NOT_IMPLEMENTED_IN_PYMBA: 'This function is not yet implemented in Pymba',
-        ERR_UNDEFINED_ERROR_CODE: 'Undefined error code',
+        ERR_COMMAND_MUST_BE_CALLED: 'Cannot get or set the value of a command feature type, call the command instead.'
     }
 
     @property