fileobj vs string vs bytes

• string/character string
  • ‘abc’
  • a sequence of Unicode code points that represent textual characters from human languages
• bytes
  • b’abc’
  • a sequence of 8 bits unsigned values
  • literal binary data
• fileobj
  • BytesIO(‘abc’) or BytesIO(b’abc’)
  • an file like object that implements .read()

A computer can only store bytes

See this stackoverflow answer