code: def sha256sum(filename):
      
      sha256 = hashlib.sha256()
      mem_view = memoryview(bytearray(128*1024))
      with open(filename, 'rb', buffering=0) as stream:
          for i in iter(lambda: stream.readinto(mem_view), 0):
              sha256.update(mem_view[:i])
      return sha256.hexdigest()
docs: Return SHA256 hash of file.