Interpolation of a str.join() via f-string

Question

Attempting to interpolate a str.join() operation:

>>> a = ["a", "b"]
>>> " ".join(a)
'a b'
>>> str = f"data -> {" ".join(a)}"
  File "<stdin>", line 1
SyntaxError: f-string: expecting '}'

f-String does not allow interpolation of such operations?

Answer 1

There is nothing stopping you from using f-interpolation on the join method.

What is happening here is that you are ending your string with the second ". That causes syntax errors because only one { is present in your f-string. Use triple quotation marks or the single quotation so that the quote character can be included in your string.

>>> f"""data -> {" ".join(a)}"""
'data -> a b'

>>> f'data -> {" ".join(a)}'
'data -> a b'