英文:
golang map prints out of order
问题
为什么地图的打印顺序是错乱的，我该如何使其按顺序打印？
package mainimport ("fmt")type monthsType struct {no inttext string}var months = map[int]string{1:"January", 2:"Fabruary", 3:"March", 4:"April", 5:"May", 6:"June",7:"July", 8:"August", 9:"September", 10:"October", 11:"Novenber", 12:"December",}func main(){for no, month := range months {fmt.Print(no)fmt.Println("-" + month)}}
打印结果为：
10-October7-July1-January9-September4-April5-May2-Fabruary12-December11-Novenber6-June8-August3-March
英文:
Why is the map printing out of order, and how do I get it in to order?
package mainimport ("fmt")type monthsType struct {no inttext string}var months = map[int]string{1:"January", 2:"Fabruary", 3:"March", 4:"April", 5:"May", 6:"June",7:"July", 8:"August", 9:"September", 10:"October", 11:"Novenber", 12:"December",}func main(){for no, month := range months {fmt.Print(no)fmt.Println("-" + month)}}
Prints out:
10-October7-July1-January9-September4-April5-May2-Fabruary12-December11-Novenber6-June8-August3-March
答案1
得分: 17
func DemoSortMap() (int, error) {
fmt.Println("使用数组按编号访问项目：")
am := [2]string{"jan", "feb"}
for i, n := range am {
fmt.Printf("%2d: %s\n", i, n)
}
fmt.Println("映射是无序的：")
mm := map[int]string{2: "feb", 1: "jan"}
for i, n := range mm {
fmt.Printf("%2d: %s\n", i, n)
}
fmt.Println("通过排序后的键列表访问项目：")
si := make([]int, 0, len(mm))
for i := range mm {
si = append(si, i)
}
sort.Ints(si)
for _, i := range si {
fmt.Printf("%2d: %s\n", i, mm[i])
}
return 0, nil
}
英文:
Code:
func DemoSortMap() (int, error) {fmt.Println("use an array to access items by number:")am := [2]string{"jan", "feb"}for i, n := range am {fmt.Printf("%2d: %s\n", i, n)}fmt.Println("maps are non-sorted:")mm := map[int]string{2: "feb", 1: "jan"}for i, n := range mm {fmt.Printf("%2d: %s\n", i, n)}fmt.Println("access items via sorted list of keys::")si := make([]int, 0, len(mm))for i := range mm {si = append(si, i)}sort.Ints(si)for _, i := range si {fmt.Printf("%2d: %s\n", i, mm[i])}return 0, nil}
(most of it stolen from M. Summerfield's book)
output:
use an array to access items by number:0: jan1: febmaps are non-sorted:2: feb1: janaccess items via sorted list of keys::1: jan2: feb
答案2
得分: 6
地图没有排序，所以您可以使用切片来对地图进行排序。Mark Summerfield的书《Go编程》在第204页解释了这一点，并且强烈推荐阅读。
英文:
Maps are not sorted so you may use a slice to sort your map. Mark Summerfield's book "Programming in Go" explains this on page 204 and is highly recommended.
答案3
得分: 1
这是非常晚的答案，但根据我所读的，地图是无序的设计，并且是随机的，因此不应依赖于顺序。
除了使用sort包与第二个地图一起使用之外，还可以使用fmt.Prinln(theMap)，它将按顺序打印地图。
>fmt：按键排序顺序打印地图
这将通常按以下方式打印地图：
map[key:valuekey:valuekey:value]
但这可能不是你想要的...
通过使用fmt.Sprint，如果需要，可以操作字符串。
例如：
s := fmt.Sprint(theMap)s1 := s[4 : len(s)-1] // 移除map[和]fmt.Println(s1)
英文:
This is very late answer, but from what I have read maps are unsorted by design, and are random as one should not rely on the order.
Besides using the sort package together with a second map, one can also use the fmt.Prinln(theMap), which will print the map sorted.
>fmt: print maps in key-sorted order
This will print the map typically as follows:
map[key:valuekey:valuekey:value]
But this might not be what you want...
By using the fmt.Sprint one can then manipulate the string if needed.
i.e.
s := fmt.Sprint(theMap)s1 := s[4 : len(s)-1] // remove map[ and ]fmt.Println(s1)
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