1#' Check the prefix of a string. 2#' 3#' Return \code{TRUE} if the string \code{str} starts with the specified 4#' \code{prefix}, otherwise return \code{FALSE}. 5#' 6#' @details 7#' With optional \code{start}, test string beginning at that position. 8#' With optional \code{end}, stop comparing string at that position. 9#' 10#' @param str A character vector. 11#' @param prefix A character vector. 12#' @param start A numeric vector. 13#' @param end A numeric vector. 14#' 15#' @return A logical vector. 16#' 17#' @references \url{https://docs.python.org/3/library/stdtypes.html#str.startswith} 18#' 19#' @seealso \code{\link{pystr_endswith}} 20#' 21#' @examples 22#' pystr_startswith("www.example.com", "www.") 23#' pystr_startswith("example.com", "www.") 24#' pystr_startswith("www.example.com", "example", 5) 25#' 26#' @export 27pystr_startswith <- function(str, prefix, start=1, end=nchar(str)) { 28 return(mapply(pystr_startswith_, str, prefix, start, end, USE.NAMES=FALSE)) 29} 30 31pystr_startswith_ <- function(str, prefix, start, end) { 32 string_to_check = substr(str, start, end) 33 start_check = 1 34 end_check = nchar(prefix) 35 letters_to_check = substr(string_to_check, start_check, end_check) 36 return(letters_to_check == prefix) 37} 38