Install osu! beatmaps (.osz) without launching osu! (but requiring a refresh), by plainly extracting them into the songs folder.

osu-install.py

from collections import namedtuple
import json
import os
import sys
import zipfile
import winreg
from winreg import HKEY_LOCAL_MACHINE, HKEY_CURRENT_USER, KEY_READ, KEY_WOW64_32KEY, KEY_WOW64_64KEY

RegistryKeyMetadata = namedtuple('RegistryKeyMetadata', ['root', 'path', 'value_name'])

OSU_USER_KEY = RegistryKeyMetadata(HKEY_CURRENT_USER, '\\'.join([
    'SOFTWARE',
    'osu!'
]), 'UninstallId')

OSU_UNINSTALL_KEY = RegistryKeyMetadata(HKEY_LOCAL_MACHINE, '\\'.join([
    'SOFTWARE',
    'Microsoft',
    'Windows',
    'CurrentVersion',
    'Uninstall',
    '{{{osuid}}}'
]), 'DisplayIcon')

OSU_PATH_END = '\\osu!.exe'

SCRIPT_SETTINGS_FILE = os.path.expanduser("~/.osuimport")

def get_osu_uninstall_id():
    with winreg.OpenKey(OSU_USER_KEY.root, OSU_USER_KEY.path, access=KEY_READ) as user_key:
        return winreg.QueryValueEx(user_key, OSU_USER_KEY.value_name)[0]

def get_osu_path(uninstall_id=None):
    if os.path.exists(SCRIPT_SETTINGS_FILE):
        try:
            with open(SCRIPT_SETTINGS_FILE, 'r') as f:
                settings = json.load(f)
            return settings.get("path")
        except:
            # Continue normal flow
            pass

    if uninstall_id is None:
        uninstall_id = get_osu_uninstall_id()
    with winreg.OpenKey(OSU_UNINSTALL_KEY.root, OSU_UNINSTALL_KEY.os.path.format(osuid=uninstall_id), access=KEY_READ) as uninstall_key:
        osu_exe = winreg.QueryValueEx(uninstall_key, OSU_UNINSTALL_KEY.value_name)[0]
    if osu_exe.endswith(OSU_PATH_END):
        return osu_exe[0:len(osu_exe) - len(OSU_PATH_END)]
    return osu_exe

def get_songs_path(osu_path):
    songs_default = os.path.join(osu_path, 'Songs')
    if os.path.exists(songs_default):
        return songs_default

    raise FileNotFoundError("Could not find songs folder inside the given osu! os.path.")

def validate_osu_path(osu_path):
    return os.path.exists(os.path.join(osu_path, 'osu!.exe')) and \
           os.path.exists(os.path.join(osu_path, 'Songs')) and \
           os.path.exists(os.path.join(osu_path, 'osu!.cfg'))

def save_osu_path(osu_path):
    if validate_osu_path(osu_path):
        with open(SCRIPT_SETTINGS_FILE, 'w') as f:
            json.dump({'path': osu_path}, f)

def main(zip_path):
    try:
        OSU_PATH = get_osu_path()
        if not validate_osu_path(OSU_PATH):
            raise FileNotFoundError()
    except FileNotFoundError as ex:
        print("I can't find Osu! installed. Type the path below; it'll be saved for future reference.")
        OSU_PATH = input("osu! installation path: ")
        if validate_osu_path(OSU_PATH):
            save_osu_path(OSU_PATH)
    
    print("Processing: {0}".format(zip_path))
    with zipfile.ZipFile(zip_path) as zf:
        zip_dst = os.path.join(get_songs_path(OSU_PATH), os.path.basename(zip_path).split(os.path.extsep)[0])
        print("Extracting to: {0}".format(zip_dst))
        if os.path.exists(zip_dst):
            print("Already exists/installed; skipping...")
        else:
            os.mkdir(zip_dst)
            zf.extractall(zip_dst)
    print("Done.")

if __name__ == '__main__':
    main(sys.argv[1])
    input("Press ENTER to exit...")