Initial commit.

.gitignore

+*~
+*.pyc
+*.pyo
+
+.idea

main.py

+from kivy.app import App
+from kivy.properties import StringProperty
+
+
+class TextClearingApp(App):
+    text = StringProperty('')
+
+    def clear_text(self):
+        self.text = ''
+
+
+if __name__ == '__main__':
+    app = TextClearingApp()
+    app.run()

textclearing.kv

+BoxLayout:
+    orientation: 'vertical'
+    TextInput:
+        text: app.text
+        on_text: app.text = self.text  # Overrride the default Kivy behavior, which is to let the properties diverge.
+    Button:
+        text: 'Clear'
+        on_press: app.clear_text()