2017-08-12 02:15 阅读 247


I've written code that is intended to print out keys and values in a map.

kvs := map[string]string{"a": "apple", "b": "banana"}
for k, v := range kvs {
    fmt.Println("%s -> %s
", k, v)

I'm expecting the output to be:

a -> apple
b -> banana

But the output is actually:

%s -> %s
a apple
%s -> %s
b banana
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2条回答 默认 最新

  • 已采纳
    dsaff82024 dsaff82024 2017-08-12 02:22

    It looks like you are trying to use string formatters, which aren't supported by fmt.Println.

    According to the godocs:

    Printf formats according to a format specifier


    Println formats using the default formats

    The following will give the output you are trying to get:

    package main
    import "fmt"
    func main() {
        kvs := map[string]string{
            "a": "apple",
            "b": "banana",
        for k, v := range kvs {
            fmt.Printf("%s -> %s
    ", k, v)

    Note that maps in Go do not have a specific ordering so you may get any arbitrary key-value pair before another.

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  • dpvmtdu364462 dpvmtdu364462 2017-08-12 02:21

    You are using the wrong printing function.

    I) Try to replace Println with Printf and it should work fine.

    II) Another option is to first format the string s := fmt.Sprintf("a %s", "string") and then print it fmt.Println(s).

    reference: Go by Example: String Formatting

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