Python Kivy writes / read the file on the SD card

Path to SD card

from jnius import autoclass  # SDcard Android

# Get path to SD card Android
try:
    Environment = autoclass('android.os.Environment')
    sdpath = Environment.get_running_app().getExternalStorageDirectory()

# Not on Android
except:
    sdpath = App.get_running_app().user_data_dir

user_data_dir also works on Android, but it relies on a /sdcard symlink which is becoming outdated. I don't know for IOS or Windows Phone though.

Copy to SD card

import shutil

sdpathfile = os.path.join(sdpath, 'filename')
shutil.copyfile(os.path.join('folder', 'filename2'), sdpathfile)

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FileChooserListView:
    id: filechooser
    path: "/your/path"

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To find a directory on your system with python, you can do something like this:

import os

for root, dirs, files in os.walk("/"):
    for name in dirs:
        if name == "DCIM":
            print(root, name)

Just be aware that it might find two or more directories named DCIM, on your sdcard and internal storage.