rename.py

import os
import sys

source_path = os.path.dirname(os.path.abspath(__file__))

# test_files_dir = os.path.join(source_path, "test_files")

if __name__ == '__main__':
    files = os.listdir(source_path)
    for file in files:
        filename, file_ext = os.path.splitext(file)
        new_ext = '.PDF'
        if file_ext == '.pdf':
            os.rename(
                os.path.join(source_path, file), # source
                os.path.join(source_path, filename + new_ext) # dest
            )
    sys.stdout.write('Done\n')