Fantastic, I believe the solution for you is this awesome project called Python-for-Android (Py4A) . not only does it allow you to run scripts on your android device. You can go one step further because the project include simple draft instructions on creating a standalone, downloadable Android APK package.
First, I would start by going to the readme section of Py4A. There is a recipes (script) that will fit your needs. The python3 recipe that allows Python3 to run as a "Stand alone" on Android.
This excerpt from Linuxjournal explains script installation on your android device:
"Running on a Smartphone
To run a Python script on your physical Android device, install SL4A together with Python for Android on your handset, then transfer your script.
To install SL4A on your physical Android device, enable the Unknown Sources option in your device's Application settings. This setting is required to enable the installation of non-Market apps on your phone. With this done, you can follow the same steps you used when installing SL4A and Python on your emulator. To speed things up a little, install Barcode Scanner from the Android Market and use it to “read” the QR Codes from your desktop screen.
Transferring Your Script to Your Handset
There are a number of ways to get your script onto a real phone. I've found the success of using something like Bluetooth connectivity or USB cabling arrangements can very much depend on the hardware on which you're running. What works on one handset, doesn't on another, and so on. Your mileage may vary depending on your actual device. When I need to transfer a file, I've come to rely on a solution that works no matter which handset I use (as long as the handset can talk to a local Wi-Fi network). What I do is switch on the OpenSSH server on my development PC running Linux, then use the AndFTP file transfer app on the handset to scp files from the desktop to the phone. AndFTP is available from the Android Market as a free download and installs in minutes. Once I connect to my desktop with AndFTP, I can navigate to a directory of my choice, mark the files that I want, then download them to my SD card on the handset.
AndFTP works well, and I've come to depend on it for all my Android file transfers (see Resources). Just be sure to transfer your scripts to /sdcard/sl4a/scripts on the phone to ensure that your script names appear within the SL4A list of scripts.
With your script file transferred to your physical device, start SL4A as before, tap your app's name and tap the run wheel. As expected, your app runs just as it did on the emulator, only faster! I haven't included a screenshot of the app running on a real phone for two reasons. First, it looks exactly the same as it did in the emulator, and second, it's running on your device, so you can take a look at it there!
Creating an APK
There's one further kink to SL4A that might interest you. The project includes draft instructions on creating a standalone, downloadable Android APK package (see Resources). Once created, the APK file bundles your custom Python script with information that allows other Android users to install Python for Android automatically onto their handsets and then run your app from the smartphone's main menu of apps. Describing the process of creating the APK likely would take another article, so I leave it to the brave among you to try out the instructions on the SL4A Wiki"