pymat: Python-style Formatting of Strings.
In Kmisc: Kevin Miscellaneous

This function allows Python-style formatting of strings, whereby text of the form {0}, {1}, ..., {n} is substituted according to the matching argument passed to .... 0 corresponds to the first argument, 1 corresponds to the second, and so on.

1	pymat(x, ..., collapse = ", ")

`x`	A string with arguments to be replaced in the form of `{0}, {1}, ..., {n}`.
`...`	Arguments to be substituted into `x`.
`collapse`	If vectors of length greater than 1 are passed to `...`, then we collapse the vectors with this separator.

pymat(
  "My favourite fruits are: {0}, {1}, and {2}.",
  "apple", "banana", "orange"
)

pymat(
  "My favourite fruits are: {0}.",
  c("apple", "banana", "orange"), collapse=", "
)