go - print without space between items

Question

fmt.Println("a","b")

I want to print the two strings without space padding, namely "ab", but the above will print "a b".

Go fmt

Do I just switch to using Printf ?

fmt.Printf("%s%s\n","a","b")

@MateuszDymczyk the starting premise is I have two strings rather than one. That said your "a"+"b" answer looks optimal. — null, Nov 20 '19 at 23:33

score 18 · Answer 1 · answered Sep 19 '14 at 11:09

18

Plain old print will work if you make the last element "\n".
It will also be easier to read if you aren't used to printf style formatting.

See here on play

fmt.Println("a","b")
fmt.Print("a","b","\n")
fmt.Printf("%s%s\n","a","b")

will print:

a b
ab
ab

answered Sep 19 '14 at 11:09

David Budworth

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Don't forget `fmt.Println("a" + "b")` – AndrewN Sep 21 '14 at 21:18
fmt.Print("a","b","\n") may hard code the \n which may by operating system specific. E.g. DOS vs Linux. fmt.Println("a" + "b") might could get around that. – null Nov 20 '19 at 23:28

score 12 · Accepted Answer · answered Sep 19 '14 at 08:03

As it can be found in the doc:

Println formats using the default formats for its operands and writes to standard output. Spaces are always added between operands and a newline is appended. It returns the number of bytes written and any write error encountered.

So you either need to do what you already said or you can concatenate the strings before printing:

fmt.Println("a"+"b")

Depending on your usecase you can use strings.Join(myStrings, "") for that purpose.

I wonder what the rationale was for making `Print` behave subtly differently to `Println` like this. — Maxpm, Sep 15 '17 at 08:43

score 2 · Answer 3 · answered Sep 19 '14 at 08:02

Println relies on doPrint(args, true, true), where first argument is addspace and second is addnewline. So Prinln ith multiple arguments will always print space.

It seems there is no call of doPrint(args, false, true) which is what you want. Printf may be a solution, Print also but you should add a newline.

score -1 · Answer 4 · answered Sep 19 '14 at 09:41

-1

You'd have to benchmark to compare performance, but I'd rather use the following than a Printf:

fmt.Println(strings.Join([]string{"a", "b"}, ""))

Remember to import "strings", and see strings.Join documentation for an explanation.

answered Sep 19 '14 at 09:41

icecrime

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fmt.Print("a","b","\n") looks much more readable. One issue may be hard coding the \n which may by operating system specific. E.g. DOS vs Linux. – null Nov 20 '19 at 23:26

score -1 · Answer 5 · answered Sep 19 '14 at 09:45

the solution in my project

package main

import "fmt"

var formatMap = map[int]string{
    0: "",
    1: "%v",
}

func Println(v ...interface{}) {
    l := len(v)
    if s, isOk := formatMap[l]; !isOk {
        for i := 0; i < len(v); i++ {
            s += "%v"
        }
        formatMap[l] = s
    }
    s := formatMap[l] + "\n"
    fmt.Printf(s, v...)
}
func main() {
    Println()
    Println("a", "b")
    Println("a", "b")
    Println("a", "b", "c", 1)
}

go - print without space between items

5 Answers5