Made abstract classes more formalised (cannot be instantiated without…

… overriding abstract methods)

src/chordparser/music/hassymbol.py

@@ -2,10 +2,13 @@
 
 
 class HasSymbol:
+    """Abstract class that contains a `Symbol`."""
+
+    _symbol: Symbol  # To be defined in concrete class
+
     @property
     def symbol(self):
-        # To be implemented in concrete class
-        raise NotImplementedError
+        return self._symbol
 
     def raise_by(self, steps=1):
         """Raise the pitch by changing only its `Symbol`.

src/chordparser/music/notationparser.py

@@ -1,9 +1,16 @@
+from abc import ABCMeta, abstractmethod
 import re
 
 
-class NotationParserTemplate:
+class NotationParserTemplate(metaclass=ABCMeta):
     """Abstract class for parsing notation."""
 
+    _pattern: str  # To be defined in concrete class
+
+    @property
+    def pattern(self):
+        return self._pattern
+
     def parse_notation(self, notation):
         regex = self._to_regex_object(notation)
         if self._invalid_notation(regex):
@@ -22,13 +29,9 @@ def _to_regex_object(self, notation):
     def _invalid_notation(self, regex):
         return not regex
 
+    @abstractmethod
     def _split_into_groups(self, regex):
-        # To be implemented in concrete class
-        raise NotImplementedError
-
-    @property
-    def pattern(self):
-        return self._pattern
+        pass
 
     def get_num_groups(self):
         regex = re.compile(self._pattern)

src/chordparser/music/note.py

@@ -74,10 +74,6 @@ def _set(self, notation):
     def letter(self):
         return self._letter
 
-    @property
-    def symbol(self):
-        return self._symbol
-
     def as_steps(self):
         """Return the number of steps of the `Note` above C.
 

src/chordparser/music/scaledegree.py

@@ -59,10 +59,6 @@ def _set(self, degree, symbol):
     def degree(self):
         return self._degree
 
-    @property
-    def symbol(self):
-        return self._symbol
-
     @classmethod
     def from_components(cls, degree, symbol=""):
         """Create a `ScaleDegree` from its degree and symbol components.