fmt.Println打印出％s之类的格式动词

Question

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

Answer 1

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

whereas

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.