How can I iterate over a string by runes in Go?

string loops go rune

Matt · Aug 8, 2013 · Viewed 78.7k times · Source

I wanted to this:

for i := 0; i < len(str); i++ {
    dosomethingwithrune(str[i]) // takes a rune
}

But it turns out that str[i] has type byte (uint8) rather than rune.

How can I iterate over the string by runes rather than bytes?

Answer

See this example from Effective Go :

for pos, char := range "日本語" {
    fmt.Printf("character %c starts at byte position %d\n", char, pos)
}

This prints :

character 日 starts at byte position 0
character 本 starts at byte position 3
character 語 starts at byte position 6

For strings, the range does more work for you, breaking out individual Unicode code points by parsing the UTF-8.