Cannon tutorial: Brush up code

- Use per class imports
- Remove string-based connections, fixing some errors introduced
  by the snake case renaming
- Add some spacing and indent main
- Use math.pi

Task-number: PYSIDE-1112
Change-Id: I2171fc9eb27f9926f32648a289df404d390ace43
Reviewed-by: Christian Tismer <[email protected]>

1 files changed, 9 insertions, 7 deletions

diff --git a/examples/widgets/tutorials/cannon/t1.py b/examples/widgets/tutorials/cannon/t1.py
index 43fea90c4..f3b4f9112 100644
--- a/examples/widgets/tutorials/cannon/t1.py
+++ b/examples/widgets/tutorials/cannon/t1.py
@@ -1,7 +1,7 @@
 
 #############################################################################
 ##
-## Copyright (C) 2016 The Qt Company Ltd.
+## Copyright (C) 2021 The Qt Company Ltd.
 ## Contact: http://www.qt.io/licensing/
 ##
 ## This file is part of the Qt for Python examples of the Qt Toolkit.
@@ -43,14 +43,16 @@
 
 
 import sys
-from PySide6 import QtWidgets
 
+from PySide6.QtWidgets import QApplication, QPushButton
 
-app = QtWidgets.QApplication(sys.argv)
 
-hello = QtWidgets.QPushButton("Hello world!")
-hello.resize(100, 30)
+if __name__ == '__main__':
+    app = QApplication(sys.argv)
 
-hello.show()
+    hello = QPushButton("Hello world!")
+    hello.resize(100, 30)
 
-sys.exit(app.exec_())
+    hello.show()
+
+    sys.exit(app.exec_())