I want to replace the nth char in the original string. I can access the nth char from the string by using chars[i], but when I assign a value to chars[i], I get an error.
package main
import "fmt"
func main() {
var chars = "abcdef"
fmt.Println(string(chars[3]))
chars[3] = "z" // is not working
}
Strings are immutable.
chars = chars[:3] + "z" + chars[4:]
This is happening because chars is actually a string and is immutable. If you declared it appropriately (as a byte slice) then you can assign to it as you're attempting. Here's an example;
package main
import "fmt"
func main() {
var chars = []byte{'a', 'b', 'c', 'd', 'e', 'f'}
fmt.Println(string(chars[3]))
fmt.Printf("%T\n", chars)
chars[3] = 'z'
fmt.Println(string(chars))
}
https://play.golang.org/p/N1sSsfIBQY
Alternately you could use reslicing as demonstrated in the other answer.
s you can just do myBytes := []byte(s)fmt.Printf("%T\n", myInstance) bit, that can be useful as %T prints the type information. In this case I added it to double check the type of chars
Using the index operator [] on a string yields byte:
A string's bytes can be accessed by integer indices 0 through len(s)-1.
so the naive approach of indexing the string directly will work only if it just happens to contain only single-byte characters.
A more solid solution is to convert the string to rune slice:
func replaceAt(s string, i int, c rune) string {
r := []rune(s)
r[i] = c
return string(r)
}
Which will work nicely with arbitrary UTF-8 input:
package main
import "fmt"
var chars = "abcdef"
var multibyte = "由汉字组成的一句话"
func main() {
v := replaceAt(chars, 3, 'z')
fmt.Println(v) // abczef
w := replaceAt(multibyte, 3, 'z')
fmt.Println(w) // 由汉子z成的一句话
}
func replaceAt(s string, i int, c rune) string {
r := []rune(s)
r[i] = c
return string(r)
}
Playground: https://go.dev/play/p/wKtYIkIXw4Z
Use slice indexing to remove the character at the index, and place a new character there instead.
package main
import "fmt"
func main() {
var chars = "abcdef"
fmt.Println(string(chars[3]))
chars = chars[:3] + "z" + chars[3+1:]
fmt.Println(string(chars[3]))
}
Output:
d
z
[:3] selects everything in the slice from the beginning up until the index 3, and [3+1:] selects everything from the index (3+1) until the end of the slice. Put the character you wanted in-between the two statements and cat them all together for the effect of replacing a character at a specific index.
If you want to replace a specific character (i.e. all (or some of) the instances of the letter 'b') you can use the strings.Replace function.
