Fix zero num_features (#374)

* use None internally to store 0 num_features

* use super set_params

* Update src/squlearn/encoding_circuit/layered_encoding_circuit.py

Co-authored-by: Florian Wieland <114916947+ProfessorNova@users.noreply.github.com>

---------

Co-authored-by: Florian Wieland <114916947+ProfessorNova@users.noreply.github.com>

Author: MoritzWillmann

src/squlearn/encoding_circuit/circuit_library/random_encoding_circuit.py

@@ -402,17 +402,7 @@ def set_params(self, **params):
         Args:
             params: Hyper-parameters and their values, e.g. ``num_qubits=2``.
         """
-        valid_params = self.get_params()
-        for key, value in params.items():
-            if key not in valid_params:
-                raise ValueError(
-                    f"Invalid parameter {key!r}. "
-                    f"Valid parameters are {sorted(valid_params)!r}."
-                )
-            try:
-                setattr(self, key, value)
-            except:
-                setattr(self, "_" + key, value)
+        super().set_params(**params)
 
         # Reset the random configuration
         self._is_config_available = False

src/squlearn/encoding_circuit/encoding_circuit_base.py

@@ -22,7 +22,7 @@ class EncodingCircuitBase(ABC):
 
     def __init__(self, num_qubits: int, num_features: int = None) -> None:
         self._num_qubits = num_qubits
-        self._num_features = num_features
+        self._num_features = num_features if num_features != 0 else None
 
         if num_features is not None:
             warnings.warn(
@@ -213,6 +213,8 @@ def set_params(self, **params) -> EncodingCircuitBase:
                     f"Invalid parameter {key!r}. "
                     f"Valid parameters are {sorted(valid_params)!r}."
                 )
+            if key == "num_features" and value == 0:
+                value = None
             try:
                 setattr(self, key, value)
             except:

src/squlearn/encoding_circuit/layered_encoding_circuit.py

@@ -2158,23 +2158,8 @@ def get_params(self, deep: bool = True) -> dict:
 
         return params
 
-    def set_params(self, **params) -> None:
-        if "encoding_circuit_str" in params:
-            self._encoding_circuit_str = params["encoding_circuit_str"]
-
-        valid_params = self.get_params()
-        for key, value in params.items():
-            if key not in valid_params:
-                raise ValueError(
-                    f"Invalid parameter {key!r}. "
-                    f"Valid parameters are {sorted(valid_params)!r}."
-                )
-
-        if "num_features" in params:
-            self._num_features = params["num_features"]
-
-        if "num_qubits" in params:
-            self._num_qubits = params["num_qubits"]
+    def set_params(self, **params):
+        super().set_params(**params)
 
         dict_layered_pqc = {}
         for key in params.keys():