Becaouse you need to give file permissions to android. what do you use to start your python app? Python3 for Android? With python3 I've never tried it, but it takes python2.7 with the recipes and then when the project is complex, you have to compile your project with python python to make it a 4 Android APK with prmission appropriate in your case reads / write filesystem.
To deploy of your python app on android you can see Buildozer
and there is also a tool that integrates graphics, you can see Kivy
Hope this help you