Refactorize code, unify class names, add documentation

form.ui

@@ -31,6 +31,13 @@
   <property name="windowTitle">
    <string>Open FM</string>
   </property>
+  <property name="windowIcon">
+   <iconset>
+    <normaloff>logo.png</normaloff>logo.png</iconset>
+  </property>
+  <property name="locale">
+   <locale language="Polish" country="Poland"/>
+  </property>
   <widget class="QWidget" name="centralwidget">
    <widget class="QWidget" name="verticalLayoutWidget">
     <property name="geometry">
@@ -45,7 +52,7 @@
      <item>
       <layout class="QHBoxLayout" name="horizontalLayout">
        <item>
-        <widget class="QListWidget" name="groupslistWidget">
+        <widget class="QListWidget" name="groupsListWidget">
          <property name="minimumSize">
           <size>
            <width>130</width>
@@ -61,14 +68,14 @@
         </widget>
        </item>
        <item>
-        <widget class="QListWidget" name="stationslistWidget"/>
+        <widget class="QListWidget" name="stationsListWidget"/>
        </item>
       </layout>
      </item>
      <item>
       <layout class="QHBoxLayout" name="horizontalLayout_2">
        <item>
-        <widget class="QToolButton" name="toolButton">
+        <widget class="QToolButton" name="playbackToolButton">
          <property name="text">
           <string>...</string>
          </property>

mainwindow.py

@@ -14,85 +14,115 @@ from ui_form import Ui_MainWindow
 import json
 import requests
 
+API_URL = "https://open.fm/radio/api/v2/ofm/stations_slug.json"
+DEFAULT_VOLUME = 70
+
 
 class MainWindow(QMainWindow):
+    """MainWindow Class."""
+
     def __init__(self, parent=None):
+        """Initialize UI, audio player and handlers."""
         super().__init__(parent)
         self.ui = Ui_MainWindow()
         self.ui.setupUi(self)
-        self.stations_slug = self.getData()
+        self.__stations_data = self.getStationsData()
         self.__player = QMediaPlayer()
         self.__audio = QAudioOutput()
         self.__player.setAudioOutput(self.__audio)
-        self.setVolume()
+        self.setVolume(DEFAULT_VOLUME)
-        self.getGroups()
+        self.printGroups()
-        self.ui.groupslistWidget.itemClicked.connect(self.getStations)
+        self.ui.groupsListWidget.itemClicked.connect(self.printStations)
-        self.ui.stationslistWidget.itemClicked.connect(self.playRadio)
+        self.ui.stationsListWidget.itemClicked.connect(self.playRadio)
-        self.ui.toolButton.clicked.connect(self.togglePlayer)
+        self.ui.playbackToolButton.clicked.connect(self.togglePlayer)
         self.ui.volumeHorizontalSlider.valueChanged.connect(self.setVolume)
         self.ui.volumeToolButton.clicked.connect(self.toggleMute)
 
-    def getGroups(self):
+    def getStationsData(self) -> dict:
-        for el in self.stations_slug["groups"]:
+        """Get JSON data from API and convert it to dict."""
-            self.ui.groupslistWidget.addItem(el["name"])
+        resp = requests.get(API_URL)
-
-    def getStations(self):
-        group = self.ui.groupslistWidget.selectedItems()[0].text()
-        group_id = None
-        for i in self.stations_slug["groups"]:
-            if i["name"] == group:
-                group_id = i["id"]
-
-        self.ui.stationslistWidget.clear()
-        for ch in self.stations_slug["channels"]:
-            if ch["group_id"] == group_id:
-                self.ui.stationslistWidget.addItem(ch["name"])
-
-    def getData(self) -> dict:
-        resp = requests.get("https://open.fm/radio/api/v2/ofm/stations_slug.json")
         if resp.status_code not in range(200, 299 + 1):
             error_box = QMessageBox.critical(
-                self, "Błąd",
+                self,
+                "Błąd",
                 f"Błąd połączenia o kodzie: {resp.status_code}",
-                QMessageBox.Cancel
+                QMessageBox.Cancel,
             )
             error_box.exec()
         else:
             return json.loads(resp.text)
 
-    def setVolume(self, volume: int = None):
+    def printGroups(self) -> None:
-        if volume is None:
+        """Print groups (categories) in groupsListWidget."""
+        self.ui.groupsListWidget.addItems(
+            [e["name"] for e in self.__stations_data["groups"]]
+        )
+
+    def printStations(self) -> None:
+        """Print stations (channels) in stationsListWidget."""
+        group = self.ui.groupsListWidget.selectedItems()[0].text()
+        group_id = None
+        for e in self.__stations_data["groups"]:
+            if e["name"] == group:
+                group_id = e["id"]
+
+        self.ui.stationsListWidget.clear()
+        self.ui.stationsListWidget.addItems(
+            [
+                e["name"]
+                for e in self.__stations_data["channels"]
+                if e["group_id"] == group_id
+            ]
+        )
+
+    def setVolume(self, volume: int = None) -> None:
+        """Set playback volume to given number or slider value."""
+        if not volume:
             volume = self.ui.volumeHorizontalSlider.value()
         self.__audio.setVolume(volume / 100)
 
-    def toggleMute(self):
+    def toggleMute(self) -> None:
+        """Toggle playback volume between 0 and DEFAULT_VOLUME."""
         if self.ui.volumeHorizontalSlider.value() == 0:
-            self.ui.volumeHorizontalSlider.setValue(70)
+            self.ui.volumeHorizontalSlider.setValue(DEFAULT_VOLUME)
-            self.ui.volumeToolButton.setIcon(QIcon.fromTheme("audio-volume-medium"))
+            self.ui.volumeToolButton.setIcon(
-            self.setVolume(70)
+                QIcon.fromTheme("audio-volume-medium")
+            )
+            self.setVolume(DEFAULT_VOLUME)
         else:
             self.ui.volumeHorizontalSlider.setValue(0)
-            self.ui.volumeToolButton.setIcon(QIcon.fromTheme("audio-volume-muted"))
+            self.ui.volumeToolButton.setIcon(
+                QIcon.fromTheme("audio-volume-muted")
+            )
             self.setVolume(0)
 
-    def playRadio(self):
+    def playRadio(self) -> None:
-        station = self.ui.stationslistWidget.selectedItems()[0].text()
+        """Play station selected by user."""
+        station = self.ui.stationsListWidget.selectedItems()[0].text()
         stream_url = None
-        for ch in self.stations_slug["channels"]:
+        for e in self.__stations_data["channels"]:
-            if ch["name"] == station:
+            if e["name"] == station:
-                stream_url = f"http://stream.open.fm/{ch['id']}"
+                stream_url = f"http://stream.open.fm/{e['id']}"
 
         self.__player.setSource(QUrl(stream_url))
-        self.ui.toolButton.setIcon(QIcon.fromTheme("media-playback-start"))
+        self.ui.playbackToolButton.setIcon(
+            QIcon.fromTheme("media-playback-start")
+        )
         self.togglePlayer()
 
-    def togglePlayer(self):
+    def togglePlayer(self) -> None:
-        if self.__player.playbackState() == QMediaPlayer.PlaybackState.PlayingState:
+        """Toggle playback (play/stop)."""
+        pb_state = QMediaPlayer.PlaybackState
+        if self.__player.playbackState() == pb_state.PlayingState:
             self.__player.stop()
-            self.ui.toolButton.setIcon(QIcon.fromTheme("media-playback-start"))
+            self.ui.playbackToolButton.setIcon(
-        elif self.__player.playbackState() == QMediaPlayer.PlaybackState.StoppedState:
+                QIcon.fromTheme("media-playback-start")
+            )
+        elif self.__player.playbackState() == pb_state.StoppedState:
             self.__player.play()
-            self.ui.toolButton.setIcon(QIcon.fromTheme("media-playback-stop"))
+            self.ui.playbackToolButton.setIcon(
+                QIcon.fromTheme("media-playback-stop")
+            )
         else:
             pass