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Comment by linkdd | Hacker News Reader

  greeting = "hello {}"
  greet = partial(str.format, greeting)
  greet("world")

How would you pass a variable format string to f"" ?

You can use variables in the formats.

  >>> flt = 1.2345
  >>> two = 2
  >>> f"{flt:.{two}f}"
  '1.23'

That is the opposite of the problem being posed. The question is how you define `greet` using f-strings.

  greet = lambda x: f"hello {x}"

  greet = lambda x: f"hello {x}"

What if "hello {x}" is not a static string but was read from somewhere else?

Surely this would not work:

  greeting = "hello {x}"
  greet = lambda x: f greeting

Something along the lines of...

    code = 'f"{input()} {x}"'

    lambda x: eval(code)

(Please don't do this)

Yes, I'll stick to using str.format :)

    code = 'f"here it is {eval(input())}"'
    (lambda: eval(code))()

k, there we go

You can’t use f-strings for that.

That was exactly my point.

That isn't the purpose for f-strings. You still have % and .format

I mean, if you're comfortable with `functools.partial`, lambdas are no great stretch:

  greet_fstring = partial(lambda _,s: f"hello {s}", greeting)

Why is the example

  greet = partial(str.format, greeting)
  greet("world")

as opposed to just

  greeting.format("world")

?

The real question is why they didn't just write:

    greet = greeting.format

It was implying you could use the str.format function as argument to other computations, something you cannot do with f-strings.

Or read the string to be formatted from a file, to name another use case.