Dynamic padding with period using f-string

Question

Given a width n, and an index i, how to generate a string of length n with x at index i, and . at the remaining indices?

For example:

Input: n = 4, i = 1
Output: ".x.."

Currently I'm doing:

"".join("x" if j == i else "." for j in range(n))

Another option:

("." * i) + "x" + ("." * (n - i - 1))

I can also do:

f"{('.' * i)}x{('.' * (n - i - 1))}"

All work, but I'm wondering if there's a way to do this with f-string, perhaps using some form of padding, as shown here?

Answer 1

You can use a mix of ljust and must multiplying to create a string

>>> f"{'.' * i}x".ljust(n, ".")
'.x..'

Or just using f strings alone by specifying a separator for the alignment

 f"{'.' * i}{'x':.<{n-i}}"