experimental persistent mixin

- still contains changes in mouduls/params ...

secop/params.py

@@ -39,10 +39,6 @@ class Accessible(HasProperties):
 
     kwds = None  # is a dict if it might be used as Override
 
-    def __init__(self, **kwds):
-        super().__init__()
-        self.init(kwds)
-
     def init(self, kwds):
         # do not use self.propertyValues.update here, as no invalid values should be
         # assigned to properties, even not before checkProperties
@@ -153,6 +149,9 @@ class Parameter(Accessible):
     handler = Property(
         '[internal] overload the standard read and write functions', ValueType(),
         export=False, default=None, settable=False)
+    persistent = Property(
+        '[internal] persistent setting', BoolType(),
+        export=False, default=False)
     initwrite = Property(
         '''[internal] write this parameter on initialization
 
@@ -165,7 +164,7 @@ class Parameter(Accessible):
     readerror = None
 
     def __init__(self, description=None, datatype=None, inherit=True, *, unit=None, constant=None, **kwds):
-        super().__init__(**kwds)
+        super().__init__()
         if datatype is not None:
             if not isinstance(datatype, DataType):
                 if isinstance(datatype, type) and issubclass(datatype, DataType):
@@ -178,6 +177,8 @@ class Parameter(Accessible):
             if 'default' in kwds:
                 self.default = datatype(kwds['default'])
 
+        self.init(kwds)  # datatype must be defined before we can treat dataset properties like fmtstr or unit
+
         if description is not None:
             self.description = inspect.cleandoc(description)
 
@@ -313,7 +314,8 @@ class Command(Accessible):
     func = None
 
     def __init__(self, argument=False, *, result=None, inherit=True, **kwds):
-        super().__init__(**kwds)
+        super().__init__()
+        self.init(kwds)
         if result or kwds or isinstance(argument, DataType) or not callable(argument):
             # normal case
             if argument is False and result: