CODEWITHSUNDEEP
arraysgo
fnr
fnr

Reputation: 9667

How to print the values of slices

I want to see the values which are in the slice. How can I print them?

projects []Project

Upvotes: 185

Views: 312538

Answers (8)

Pylinux
Pylinux

Reputation: 11836

Quick to write

fmt.Printf("%+q", arr) which will print

["some" "values" "list"]

https://play.golang.org/p/XHfkENNQAKb

Valid JSON

json.NewEncoder(os.Stdout).Encode(arr) which will print

["hello","world"]

https://go.dev/play/p/JNZjAAYf2sB

Upvotes: 48

user12817546
user12817546

Reputation:

You could use a for loop to print the []Project as shown in @VonC excellent answer.

package main

import "fmt"

type Project struct{ name string }

func main() {
    projects := []Project{{"p1"}, {"p2"}}
    for i := range projects {
        p := projects[i]
        fmt.Println(p.name) //p1, p2
    }
}

Upvotes: 4

Inanc Gumus
Inanc Gumus

Reputation: 27941

I wrote a package named Pretty Slice. You can use it to visualize slices, and their backing arrays, etc.

package main

import pretty "github.com/inancgumus/prettyslice"

func main() {
    nums := []int{1, 9, 5, 6, 4, 8}
    odds := nums[:3]
    evens := nums[3:]

    nums[1], nums[3] = 9, 6
    pretty.Show("nums", nums)
    pretty.Show("odds : nums[:3]", odds)
    pretty.Show("evens: nums[3:]", evens)
}

This code is going produce and output like this one:

enter image description here

For more details, please read: https://github.com/inancgumus/prettyslice

Upvotes: 6

Gamelub
Gamelub

Reputation: 71

If you want to view the information in a slice in the same format that you'd use to type it in (something like ["one", "two", "three"]), here's a code example showing how to do that:

package main

import (
    "fmt"
    "strings"
)

func main() {
    test := []string{"one", "two", "three"}     // The slice of data
    semiformat := fmt.Sprintf("%q\n", test)     // Turn the slice into a string that looks like ["one" "two" "three"]
    tokens := strings.Split(semiformat, " ")    // Split this string by spaces
    fmt.Printf(strings.Join(tokens, ", "))      // Join the Slice together (that was split by spaces) with commas
}

Go Playground

Upvotes: 7

Eddie Curtis
Eddie Curtis

Reputation: 1237

If you just want to see the values of an array without brackets, you can use a combination of fmt.Sprint() and strings.Trim()

a := []string{"a", "b"}
fmt.Print(strings.Trim(fmt.Sprint(a), "[]"))
fmt.Print(a)

Returns:

a b
[a b]

Be aware though that with this solution any leading brackets will be lost from the first value and any trailing brackets will be lost from the last value

a := []string{"[a]", "[b]"}
fmt.Print(strings.Trim(fmt.Sprint(a), "[]")
fmt.Print(a)

Returns:

a] [b
[[a] [b]]

For more info see the documentation for strings.Trim()

Upvotes: 7

akond
akond

Reputation: 16060

fmt.Printf() is fine, but sometimes I like to use pretty print package.

import "github.com/kr/pretty"
pretty.Print(...)

Upvotes: 4

jgillich
jgillich

Reputation: 76329

For a []string, you can use strings.Join():

s := []string{"foo", "bar", "baz"}
fmt.Println(strings.Join(s, ", "))
// output: foo, bar, baz

Upvotes: 50

VonC
VonC

Reputation: 1328002

You can try the %v, %+v or %#v verbs of go fmt:

fmt.Printf("%v", projects)

If your array (or here slice) contains struct (like Project), you will see their details.
For more precision, you can use %#v to print the object using Go-syntax, as for a literal:

%v  the value in a default format.
    when printing structs, the plus flag (%+v) adds field names
%#v a Go-syntax representation of the value

For basic types, fmt.Println(projects) is enough.

Note: for a slice of pointers, that is []*Project (instead of []Project), you are better off defining a String() method in order to display exactly what you want to see (or you will see only pointer address).
See this play.golang example.

Upvotes: 290

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