import os

lib_dir = r'\\alex.sl.int\alex-slsync\library\County Record Library'

for doctype in os.listdir(lib_dir):
    folder = os.path.join(lib_dir, doctype)

    if os.path.exists(folder) and os.path.isdir(folder):
        print('Renaming files in %s' % doctype)
        for old_name in os.listdir(folder):
            old_path = os.path.join(folder, old_name)

            split_idx = old_name.find('.')
            new_name = old_name[:split_idx].upper()
            ext = old_name[split_idx:]

            new_name += ext
            new_path = os.path.join(folder, new_name)
            os.rename(old_path, new_path)
            print('  Renamed %s to %s' % (old_name, new_name))

print('Done renaming files in library')