Let's concatenate strings.

  a + b
  f"{a}{b}"
  "".join([a, b])
  "{}{}".format(a, b)

If a == b, then you can also, which itself is a bit ridiculous:

  a * 2

Is mentioning StringIO considered cheating?

I would feel the Zen if Python would have a separate concatenation operator, it could be even the same for strings and lists. Lack of the operator in popular languages is my pet peeve.