如何进行For-Else循环（使用其他语言的Else-Else）？

Question

A while back I have read/seen that you can do a For-Else loop in Go, but now I cannot find the correct syntax anymore. I find it a very useful construct, and would like to have it in my toolbelt.

For a python example of what I mean see http://www.yourownlinux.com/2016/12/python-while-else-loop-break-continue-statement.html .

while myVar <= 10 :
     myVar == myNum :
             print 'Breaking out of the loop'
             break
     print 'This number = ' + str(myVar)
     myVar += 1
 else:
     print 'Break statement is executed, printing "else" block'

Answer 1

Python 3.7.4 documentation

8.2. The while statement

The while statement is used for repeated execution as long as an expression is true:

while_stmt ::=  "while" expression ":" suite
                ["else" ":" suite]

This repeatedly tests the expression and, if it is true, executes the first suite; if the expression is false (which may be the first time it is tested) the suite of the else clause, if present, is executed and the loop terminates.

A break statement executed in the first suite terminates the loop without executing the else clause’s suite.

---

Your code:

while myVar <= 10 :
     myVar == myNum :
             print 'Breaking out of the loop'
             break
     print 'This number = ' + str(myVar)
     myVar += 1
 else:
     print 'Break statement is executed, printing "else" block'

---

Your example, in Go,

package main

import (
    "fmt"
    "strconv"
)

func main() {
    var myNum int = 7
    var myVar int = 0
    for {
        if myVar <= 10 {
            if myVar == myNum {
                fmt.Println("Breaking out of the loop")
                break
            }
            fmt.Println("This number = " + strconv.Itoa(myVar))
            myVar++
        } else {
            fmt.Println(`"while" "else" block`)
            break
        }
    }
}

Playground: https://play.golang.org/p/MkwhWfL4cr6

Output:

This number = 0
This number = 1
This number = 2
This number = 3
This number = 4
This number = 5
This number = 6
Breaking out of the loop