#df <- read.table("city.txt", header = TRUE, stringsAsFactors=FALSE)
df <- structure(list(City = c("a", "b", "e", "a", "e", "b", "b", "a"
  ), Score = c(3L, 3L, 2L, 4L, 5L, 1L, 3L, 5L)), .Names = c("City", 
  "Score"), class = "data.frame", row.names = c(NA, -8L))
retval <- lapply(unique(df$City), function(city) {
  df$Score[which(df$City == city)]
})
names(retval) <- unique(df$City)
retval