import os

dir = input("Directory: ")
files = [f for f in os.listdir(dir) if os.path.isfile(os.path.join(dir, f))]

for file in files:
    os.rename(
        os.path.join(dir, file),
        os.path.join(dir, str(os.path.getsize(os.path.join(dir, file)))),
    )