golang语言渐入佳境[17]-mapping表

//1、声明map的方式1var map1 map[string]string//2、声明map的方式2map2 := make(map[string]string)//3、map中key可以是：int、float、bool、string、数组//	一定不可以是：切片、函数、mapvar m1 map[int]stringvar m2 map[float64]stringvar m3 map[bool]stringvar m4 map[string]string

var country = map[string]string{	"China":  "Beijing",	"Japan":  "Tokyo",	"India":  "New Delhi",	"France": "Paris",	"Italy":  "Rome",}fmt.Println(country)//短变量声明初始化方式rating := map[string]float64{"c": 5, "Go": 4.5, "Python": 4.5, "C++": 3}fmt.Println(rating)

countryMap := make(map[string]string)countryMap["China"] = "Beijing"countryMap["Japan"] = "Tokyo"countryMap["India"] = "New Delhi"countryMap["France"] = "Paris"countryMap["Italy"] = "Rome"

for k, v := range countryMap {  fmt.Println("国家", k, "首都", v)}

for _, v := range countryMap {  fmt.Println("国家",  "首都", v)}

for k := range countryMap {  fmt.Println("国家",  k , "首都", countryMap[k])}

value , ok := countryMap["England"]fmt.Printf("%q \n" , value)fmt.Printf("%T , %v \n" , ok , ok)if ok {  fmt.Println("首都：" , value)} else {  fmt.Println("首都信息未检索到！")}//第二种方式if value ,ok :=countryMap["USA"];ok {  fmt.Println("首都：" , value)} else {  fmt.Println("首都信息未检索到！")}

package mainimport "fmt"func main() {//1、声明时同时初始化var country = map[string]string{"China":  "Beijing","Japan":  "Tokyo","India":  "New Delhi","France": "Paris","Italy":  "Rome",	}	fmt.Println(country)//短变量声明初始化方式	rating := map[string]float64{"c": 5, "Go": 4.5, "Python": 4.5, "C++": 3}	fmt.Println(rating)//2、创建map后再赋值	countryMap := make(map[string]string)	countryMap["China"] = "Beijing"	countryMap["Japan"] = "Tokyo"	countryMap["India"] = "New Delhi"	countryMap["France"] = "Paris"	countryMap["Italy"] = "Rome"//	3、遍历map（无序）//	(1)、key 、value都遍历for k, v := range countryMap {		fmt.Println("国家", k, "首都", v)	}	fmt.Println("-----------")//(2)、只展示valuefor _, v := range countryMap {		fmt.Println("国家",  "首都", v)	}	fmt.Println("-----------")//(3)、只展示keyfor k := range countryMap {		fmt.Println("国家",  k , "首都", countryMap[k])	}	fmt.Println("-----------")//4、查看元素是否在map中存在	value , ok := countryMap["England"]	fmt.Printf("%q \n" , value)	fmt.Printf("%T , %v \n" , ok , ok)if ok {		fmt.Println("首都：" , value)	} else {		fmt.Println("首都信息未检索到！")	}//或者if value ,ok :=countryMap["USA"];ok {		fmt.Println("首都：" , value)	} else {		fmt.Println("首都信息未检索到！")	}}

package mainimport "fmt"func main() {//1、声明并初始化一个map	map1 := map[string]string {"element":"div","width" :"100px","height":"200px","border":"solid","background":"none",	}//2、根据key删除map中的某个元素	fmt.Println("删除前：",map1)if _,ok := map1["background"]; ok {delete(map1 , "background")	}	fmt.Println("删除后：",map1)//3、清空map//map1 = map[string]string{}	map1 = make(map[string]string)	fmt.Println("清空后：",map1)}