{"id":1047,"date":"2026-08-16T17:18:01","date_gmt":"2026-08-16T17:18:01","guid":{"rendered":"https:\/\/www.devopsschool.com\/tutorials\/?p=1047"},"modified":"2026-08-16T18:49:28","modified_gmt":"2026-08-16T18:49:28","slug":"go-tutorial-go-blank-identifier-_-master-tutorial","status":"publish","type":"post","link":"https:\/\/www.devopsschool.com\/tutorials\/go-tutorial-go-blank-identifier-_-master-tutorial\/","title":{"rendered":"Go Tutorial: Go Blank Identifier _ \u2014 Master Tutorial"},"content":{"rendered":"\n

The underscore:<\/p>\n\n\n\n

_\n<\/code><\/pre>\n\n\n\n
is called the blank identifier<\/strong> in Go.<\/p>\n\n\n\n
The easiest way to understand it is:<\/p>\n\n\n\n
\n
_<\/code> means: \u201cGo gives me this value, but I intentionally do not want to use it.\u201d<\/strong><\/p>\n<\/blockquote>\n\n\n\n
It is not a normal variable. You can put values into<\/strong> _<\/code>, but you cannot get values back out of<\/strong> _<\/code>.<\/p>\n\n\n\n
\n\n\n\n
1. Why Does Go Need _<\/code>?<\/h1>\n\n\n\n
Go is strict about unused variables.<\/p>\n\n\n\n
This code will not compile:<\/p>\n\n\n\n
package main\n\nfunc main() {\n    name := \"Rajesh\"\n}\n<\/code><\/pre>\n\n\n\n
Go gives an error similar to:<\/p>\n\n\n\n
declared and not used: name\n<\/code><\/pre>\n\n\n\n
Go wants you to either:<\/p>\n\n\n\n
    \n
  1. use the value, or<\/li>\n\n\n\n
  2. explicitly tell Go that you want to ignore it.<\/li>\n<\/ol>\n\n\n\n
    That is one major purpose of _<\/code>.<\/p>\n\n\n\n
    \n\n\n\n
    2. Most Common Use: range<\/code> Loops<\/h1>\n\n\n\n
    Consider:<\/p>\n\n\n\n
    menu := []string{\"Pizza\", \"Burger\", \"Pasta\"}\n<\/code><\/pre>\n\n\n\n
    When you use range<\/code> on a slice, Go can return two values:<\/p>\n\n\n\n
    for index, value := range menu {\n}\n<\/code><\/pre>\n\n\n\n
    Example:<\/p>\n\n\n\n
    package main\n\nimport \"fmt\"\n\nfunc main() {\n    menu := []string{\"Pizza\", \"Burger\", \"Pasta\"}\n\n    for index, item := range menu {\n        fmt.Println(index, item)\n    }\n}\n<\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    0 Pizza\n1 Burger\n2 Pasta\n<\/code><\/pre>\n\n\n\n
    So:<\/p>\n\n\n\n
    range menu\n   \u2502\n   \u251c\u2500\u2500 index\n   \u2502\n   \u2514\u2500\u2500 value\n<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    3. Ignore the Index with _<\/code><\/h1>\n\n\n\n
    Suppose you only care about the food name.<\/p>\n\n\n\n
    Instead of:<\/p>\n\n\n\n
    for index, item := range menu {\n<\/code><\/pre>\n\n\n\n
    use:<\/p>\n\n\n\n
    for _, item := range menu {\n<\/code><\/pre>\n\n\n\n
    Example:<\/p>\n\n\n\n
    package main\n\nimport \"fmt\"\n\nfunc main() {\n    menu := []string{\"Pizza\", \"Burger\", \"Pasta\"}\n\n    for _, item := range menu {\n        fmt.Println(item)\n    }\n}\n<\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    Pizza\nBurger\nPasta\n<\/code><\/pre>\n\n\n\n
    Meaning:<\/p>\n\n\n\n
    for _, item := range menu {\n<\/code><\/pre>\n\n\n\n
    can be read as:<\/p>\n\n\n\n
    for IGNORE_INDEX, item := range menu\n<\/code><\/pre>\n\n\n\n
    or mentally:<\/p>\n\n\n\n
    I don't care, item\n       \u2193       \u2193\n       _      item\n<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    4. If You Only Need the Index<\/h1>\n\n\n\n
    Interestingly, if you only need the index, you don’t need _<\/code>.<\/p>\n\n\n\n
    You can write:<\/p>\n\n\n\n
    for index := range menu {\n    fmt.Println(index)\n}\n<\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    0\n1\n2\n<\/code><\/pre>\n\n\n\n
    You could technically write:<\/p>\n\n\n\n
    for index, _ := range menu {\n<\/code><\/pre>\n\n\n\n
    but that is unnecessary.<\/p>\n\n\n\n
    Prefer:<\/p>\n\n\n\n
    for index := range menu {\n<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    5. _<\/code> with Functions Returning Multiple Values<\/h1>\n\n\n\n
    This is another extremely common use.<\/p>\n\n\n\n
    Suppose a function returns two values:<\/p>\n\n\n\n
    func calculate() (int, int) {\n    return 10, 20\n}\n<\/code><\/pre>\n\n\n\n
    Normally:<\/p>\n\n\n\n
    a, b := calculate()\n<\/code><\/pre>\n\n\n\n
    Example:<\/p>\n\n\n\n
    package main\n\nimport \"fmt\"\n\nfunc calculate() (int, int) {\n    return 10, 20\n}\n\nfunc main() {\n    a, b := calculate()\n\n    fmt.Println(a)\n    fmt.Println(b)\n}\n<\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    10\n20\n<\/code><\/pre>\n\n\n\n
    But suppose you only want the first value.<\/p>\n\n\n\n
    Use:<\/p>\n\n\n\n
    a, _ := calculate()\n<\/code><\/pre>\n\n\n\n
    Full example:<\/p>\n\n\n\n
    package main\n\nimport \"fmt\"\n\nfunc calculate() (int, int) {\n    return 10, 20\n}\n\nfunc main() {\n    a, _ := calculate()\n\n    fmt.Println(a)\n}\n<\/code><\/pre>\n\n\n\n
    Here:<\/p>\n\n\n\n
    calculate()\n     \u2502\n     \u251c\u2500\u2500 10 \u2192 a\n     \u2502\n     \u2514\u2500\u2500 20 \u2192 _\n              ignored\n<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    6. _<\/code> with Go Errors<\/h1>\n\n\n\n
    Go functions frequently return:<\/p>\n\n\n\n
    value, error\n<\/code><\/pre>\n\n\n\n
    For example:<\/p>\n\n\n\n
    number, err := strconv.Atoi(\"100\")\n<\/code><\/pre>\n\n\n\n
    strconv.Atoi()<\/code> converts a string to an integer.<\/p>\n\n\n\n
    Example:<\/p>\n\n\n\n
    package main\n\nimport (\n    \"fmt\"\n    \"strconv\"\n)\n\nfunc main() {\n    number, err := strconv.Atoi(\"100\")\n\n    if err != nil {\n        fmt.Println(\"Error:\", err)\n        return\n    }\n\n    fmt.Println(number)\n}\n<\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    100\n<\/code><\/pre>\n\n\n\n
    Sometimes you may see:<\/p>\n\n\n\n
    number, _ := strconv.Atoi(\"100\")\n<\/code><\/pre>\n\n\n\n
    This means:<\/p>\n\n\n\n
    number \u2192 keep\nerror  \u2192 ignore\n<\/code><\/pre>\n\n\n\n
    Example:<\/p>\n\n\n\n
    package main\n\nimport (\n    \"fmt\"\n    \"strconv\"\n)\n\nfunc main() {\n    number, _ := strconv.Atoi(\"100\")\n\n    fmt.Println(number)\n}\n<\/code><\/pre>\n\n\n\n
    However, be careful.<\/p>\n\n\n\n
    Bad practice<\/h2>\n\n\n\n
    number, _ := strconv.Atoi(input)\n<\/code><\/pre>\n\n\n\n
    If input<\/code> could be invalid, you are throwing away useful error information.<\/p>\n\n\n\n
    Usually prefer:<\/p>\n\n\n\n
    number, err := strconv.Atoi(input)\n\nif err != nil {\n    fmt.Println(\"Invalid number\")\n    return\n}\n<\/code><\/pre>\n\n\n\n
    Important Rule<\/h3>\n\n\n\n
    Using _<\/code> for an error is legal:<\/p>\n\n\n\n
    value, _ := something()\n<\/code><\/pre>\n\n\n\n
    but don’t blindly ignore errors.<\/p>\n\n\n\n
    \n\n\n\n
    7. _<\/code> with Map Lookup<\/h1>\n\n\n\n
    Maps have a very useful two-value lookup syntax.<\/p>\n\n\n\n
    Consider:<\/p>\n\n\n\n
    ages := map[string]int{\n    \"Rajesh\": 42,\n    \"John\":   35,\n}\n<\/code><\/pre>\n\n\n\n
    You can do:<\/p>\n\n\n\n
    age, exists := ages[\"Rajesh\"]\n<\/code><\/pre>\n\n\n\n
    Example:<\/p>\n\n\n\n
    package main\n\nimport \"fmt\"\n\nfunc main() {\n    ages := map[string]int{\n        \"Rajesh\": 42,\n        \"John\":   35,\n    }\n\n    age, exists := ages[\"Rajesh\"]\n\n    fmt.Println(age)\n    fmt.Println(exists)\n}\n<\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    42\ntrue\n<\/code><\/pre>\n\n\n\n
    Suppose you don’t care about the age.<\/p>\n\n\n\n
    You only want to know:<\/p>\n\n\n\n
    \n
    Does \"Rajesh\"<\/code> exist in the map?<\/p>\n<\/blockquote>\n\n\n\n
    Use:<\/p>\n\n\n\n
    _, exists := ages[\"Rajesh\"]\n<\/code><\/pre>\n\n\n\n
    Example:<\/p>\n\n\n\n
    package main\n\nimport \"fmt\"\n\nfunc main() {\n    ages := map[string]int{\n        \"Rajesh\": 42,\n    }\n\n    _, exists := ages[\"Rajesh\"]\n\n    if exists {\n        fmt.Println(\"Rajesh exists\")\n    }\n}\n<\/code><\/pre>\n\n\n\n
    Very common Go pattern:<\/p>\n\n\n\n
    if _, exists := ages[\"Rajesh\"]; exists {\n    fmt.Println(\"Found\")\n}\n<\/code><\/pre>\n\n\n\n
    Think of it as:<\/p>\n\n\n\n
    ages[\"Rajesh\"]\n      \u2502\n      \u251c\u2500\u2500 value \u2192 _\n      \u2502           ignored\n      \u2502\n      \u2514\u2500\u2500 exists \u2192 true\/false\n<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    8. _<\/code> with Type Assertions<\/h1>\n\n\n\n
    Go type assertions can also return two values:<\/p>\n\n\n\n
    value, ok := something.(string)\n<\/code><\/pre>\n\n\n\n
    For example:<\/p>\n\n\n\n
    package main\n\nimport \"fmt\"\n\nfunc main() {\n    var data any = \"Hello\"\n\n    value, ok := data.(string)\n\n    fmt.Println(value)\n    fmt.Println(ok)\n}\n<\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    Hello\ntrue\n<\/code><\/pre>\n\n\n\n
    Suppose you only want to know whether data<\/code> contains a string.<\/p>\n\n\n\n
    Use:<\/p>\n\n\n\n
    _, ok := data.(string)\n<\/code><\/pre>\n\n\n\n
    Example:<\/p>\n\n\n\n
    package main\n\nimport \"fmt\"\n\nfunc main() {\n    var data any = \"Hello\"\n\n    _, ok := data.(string)\n\n    if ok {\n        fmt.Println(\"data contains a string\")\n    }\n}\n<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    9. _<\/code> with Multiple Assignments<\/h1>\n\n\n\n
    The blank identifier can appear anywhere in an assignment.<\/p>\n\n\n\n
    Example function:<\/p>\n\n\n\n
    func values() (int, int, int) {\n    return 10, 20, 30\n}\n<\/code><\/pre>\n\n\n\n
    You can ignore the middle value:<\/p>\n\n\n\n
    a, _, c := values()\n<\/code><\/pre>\n\n\n\n
    Full example:<\/p>\n\n\n\n
    package main\n\nimport \"fmt\"\n\nfunc values() (int, int, int) {\n    return 10, 20, 30\n}\n\nfunc main() {\n    a, _, c := values()\n\n    fmt.Println(a)\n    fmt.Println(c)\n}\n<\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    10\n30\n<\/code><\/pre>\n\n\n\n
    Visual:<\/p>\n\n\n\n
    values()\n\n10    20    30\n\u2193      \u2193     \u2193\na      _     c\n       \u2502\n     ignored\n<\/code><\/pre>\n\n\n\n
    You can ignore several:<\/p>\n\n\n\n
    _, _, c := values()\n<\/code><\/pre>\n\n\n\n
    or:<\/p>\n\n\n\n
    a, _, _ := values()\n<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    10. _<\/code> with Function Parameters<\/h1>\n\n\n\n
    You can also use _<\/code> for a function parameter that you intentionally don’t need.<\/p>\n\n\n\n
    For example:<\/p>\n\n\n\n
    func calculate(_, b int) int {\n    return b * 2\n}\n<\/code><\/pre>\n\n\n\n
    Full example:<\/p>\n\n\n\n
    package main\n\nimport \"fmt\"\n\nfunc calculate(_, b int) int {\n    return b * 2\n}\n\nfunc main() {\n    result := calculate(10, 20)\n\n    fmt.Println(result)\n}\n<\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    40\n<\/code><\/pre>\n\n\n\n
    The first argument:<\/p>\n\n\n\n
    10\n<\/code><\/pre>\n\n\n\n
    was received but intentionally ignored.<\/p>\n\n\n\n
    This is less common in beginner programs but can be useful with callbacks or interfaces where a function signature requires parameters you don’t need.<\/p>\n\n\n\n
    \n\n\n\n
    11. _<\/code> with range<\/code> over Maps<\/h1>\n\n\n\n
    Suppose:<\/p>\n\n\n\n
    prices := map[string]float64{\n    \"Small\":  2.50,\n    \"Medium\": 3.50,\n    \"Large\":  4.50,\n}\n<\/code><\/pre>\n\n\n\n
    A map range provides:<\/p>\n\n\n\n
    for key, value := range prices {\n<\/code><\/pre>\n\n\n\n
    Example:<\/p>\n\n\n\n
    for size, cost := range prices {\n    fmt.Println(size, cost)\n}\n<\/code><\/pre>\n\n\n\n
    You might get:<\/p>\n\n\n\n
    Small 2.5\nMedium 3.5\nLarge 4.5\n<\/code><\/pre>\n\n\n\n
    If you only care about the price:<\/p>\n\n\n\n
    for _, cost := range prices {\n    fmt.Println(cost)\n}\n<\/code><\/pre>\n\n\n\n
    Here:<\/p>\n\n\n\n
    key   \u2192 _\nvalue \u2192 cost\n<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    12. Your Original Menu Example<\/h1>\n\n\n\n
    Your screenshot contained something like:<\/p>\n\n\n\n
    func printMenu() {\n    for _, item := range menu {\n        fmt.Println(item.name)\n\n        for size, cost := range item.prices {\n            fmt.Printf(\"\\t%10s%10.2f\\n\", size, cost)\n        }\n    }\n}\n<\/code><\/pre>\n\n\n\n
    Let’s break it down.<\/p>\n\n\n\n
    The outer loop:<\/p>\n\n\n\n
    for _, item := range menu {\n<\/code><\/pre>\n\n\n\n
    means:<\/p>\n\n\n\n
    menu\n \u2502\n \u251c\u2500\u2500 index \u2192 _       ignored\n \u2502\n \u2514\u2500\u2500 value \u2192 item    used\n<\/code><\/pre>\n\n\n\n
    The programmer doesn’t need:<\/p>\n\n\n\n
    0\n1\n2\n3\n<\/code><\/pre>\n\n\n\n
    They only need each menu item.<\/p>\n\n\n\n
    The inner loop:<\/p>\n\n\n\n
    for size, cost := range item.prices {\n<\/code><\/pre>\n\n\n\n
    uses both returned values:<\/p>\n\n\n\n
    size \u2192 Small\ncost \u2192 2.50\n<\/code><\/pre>\n\n\n\n
    So _<\/code> is unnecessary there.<\/p>\n\n\n\n
    \n\n\n\n
    13. Blank Imports: import _ \"package\"<\/code><\/h1>\n\n\n\n
    Now we get into an important advanced use.<\/p>\n\n\n\n
    Sometimes you will see:<\/p>\n\n\n\n
    import _ \"some\/package\"\n<\/code><\/pre>\n\n\n\n
    For example:<\/p>\n\n\n\n
    import _ \"github.com\/lib\/pq\"\n<\/code><\/pre>\n\n\n\n
    This is called a blank import<\/strong>.<\/p>\n\n\n\n
    Normally Go does not allow you to import a package without using it.<\/p>\n\n\n\n
    This produces an error:<\/p>\n\n\n\n
    import \"github.com\/lib\/pq\"\n<\/code><\/pre>\n\n\n\n
    if you never reference pq<\/code>.<\/p>\n\n\n\n
    But sometimes you don’t need to call functions from that package.<\/p>\n\n\n\n
    You only want Go to execute the package’s:<\/p>\n\n\n\n
    func init()\n<\/code><\/pre>\n\n\n\n
    logic.<\/p>\n\n\n\n
    Then you import it using:<\/p>\n\n\n\n
    import _ \"github.com\/lib\/pq\"\n<\/code><\/pre>\n\n\n\n
    Meaning:<\/p>\n\n\n\n
    \n
    Import this package for its side effects<\/strong>, but don’t give me a package identifier to use directly.<\/p>\n<\/blockquote>\n\n\n\n
    This has historically been common with things like database drivers, image formats, and plugins.<\/p>\n\n\n\n
    Conceptually:<\/p>\n\n\n\n
    import _ \"some\/package\"\n          \u2502\n          \u2193\n      load package\n          \u2502\n          \u2193\n      run init()\n          \u2502\n          \u2193\ndon't reference package directly\n<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    14. _<\/code> for Interface Implementation Checks<\/h1>\n\n\n\n
    This is a very useful advanced Go pattern.<\/p>\n\n\n\n
    Suppose you have an interface:<\/p>\n\n\n\n
    type Speaker interface {\n    Speak()\n}\n<\/code><\/pre>\n\n\n\n
    And a struct:<\/p>\n\n\n\n
    type Person struct{}\n<\/code><\/pre>\n\n\n\n
    With:<\/p>\n\n\n\n
    func (p Person) Speak() {\n    fmt.Println(\"Hello\")\n}\n<\/code><\/pre>\n\n\n\n
    Developers sometimes write:<\/p>\n\n\n\n
    var _ Speaker = Person{}\n<\/code><\/pre>\n\n\n\n
    Full example:<\/p>\n\n\n\n
    package main\n\nimport \"fmt\"\n\ntype Speaker interface {\n    Speak()\n}\n\ntype Person struct{}\n\nfunc (p Person) Speak() {\n    fmt.Println(\"Hello\")\n}\n\nvar _ Speaker = Person{}\n\nfunc main() {\n    p := Person{}\n    p.Speak()\n}\n<\/code><\/pre>\n\n\n\n
    What does this do?<\/p>\n\n\n\n
    It tells the Go compiler:<\/p>\n\n\n\n
    \n
    Make sure Person<\/code> implements Speaker<\/code>.<\/p>\n<\/blockquote>\n\n\n\n
    But we don’t actually need to create a useful variable.<\/p>\n\n\n\n
    So the result is assigned to:<\/p>\n\n\n\n
    _\n<\/code><\/pre>\n\n\n\n
    If Person<\/code> stops implementing Speaker<\/code>, the program fails to compile.<\/p>\n\n\n\n
    You will often see:<\/p>\n\n\n\n
    var _ MyInterface = (*MyType)(nil)\n<\/code><\/pre>\n\n\n\n
    This is called a compile-time interface assertion<\/strong>.<\/p>\n\n\n\n
    \n\n\n\n
    15. _ = variable<\/code><\/h1>\n\n\n\n
    You may occasionally see:<\/p>\n\n\n\n
    _ = value\n<\/code><\/pre>\n\n\n\n
    For example:<\/p>\n\n\n\n
    func main() {\n    name := \"Rajesh\"\n\n    _ = name\n}\n<\/code><\/pre>\n\n\n\n
    This compiles.<\/p>\n\n\n\n
    Without:<\/p>\n\n\n\n
    _ = name\n<\/code><\/pre>\n\n\n\n
    Go would complain:<\/p>\n\n\n\n
    declared and not used: name\n<\/code><\/pre>\n\n\n\n
    So this:<\/p>\n\n\n\n
    _ = name\n<\/code><\/pre>\n\n\n\n
    basically tells Go:<\/p>\n\n\n\n
    \n
    Yes, I know name<\/code> exists. I am intentionally not using it.<\/p>\n<\/blockquote>\n\n\n\n
    This can occasionally be useful while experimenting or debugging.<\/p>\n\n\n\n
    But don’t make this a habit.<\/p>\n\n\n\n
    Instead of:<\/p>\n\n\n\n
    name := getName()\n_ = name\n<\/code><\/pre>\n\n\n\n
    usually remove the unnecessary variable if you don’t need it.<\/p>\n\n\n\n
    \n\n\n\n
    16. _<\/code> Is NOT a Normal Variable<\/h1>\n\n\n\n
    This point is extremely important.<\/p>\n\n\n\n
    You can assign:<\/p>\n\n\n\n
    _ = 100\n<\/code><\/pre>\n\n\n\n
    You can assign again:<\/p>\n\n\n\n
    _ = \"Hello\"\n<\/code><\/pre>\n\n\n\n
    And again:<\/p>\n\n\n\n
    _ = true\n<\/code><\/pre>\n\n\n\n
    But you cannot do:<\/p>\n\n\n\n
    fmt.Println(_)\n<\/code><\/pre>\n\n\n\n
    This is invalid.<\/p>\n\n\n\n
    Why?<\/p>\n\n\n\n
    Because _<\/code> doesn’t store a value that you can retrieve.<\/p>\n\n\n\n
    Think about _<\/code> as a trash bin<\/strong>:<\/p>\n\n\n\n
    100 \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510\n            \u2502\n\"Hello\" \u2500\u2500\u2500\u2500\u253c\u2500\u2500\u2192  _\n            \u2502     \ud83d\uddd1\ufe0f\ntrue \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n\nNothing comes back out.\n<\/code><\/pre>\n\n\n\n
    So:<\/p>\n\n\n\n
    _ = 100\n<\/code><\/pre>\n\n\n\n
    means:<\/p>\n\n\n\n
    \n
    throw away 100<\/code>.<\/p>\n<\/blockquote>\n\n\n\n
    It does NOT mean:<\/p>\n\n\n\n
    \n
    create a variable named _<\/code> containing 100<\/code>.<\/p>\n<\/blockquote>\n\n\n\n
    \n\n\n\n
    17. _<\/code> Can Be Used Multiple Times<\/h1>\n\n\n\n
    Unlike normal variable names, _<\/code> can appear many times:<\/p>\n\n\n\n
    _, _, result := values()\n<\/code><\/pre>\n\n\n\n
    For example:<\/p>\n\n\n\n
    func data() (string, int, bool) {\n    return \"Rajesh\", 42, true\n}\n\nfunc main() {\n    _, _, active := data()\n\n    fmt.Println(active)\n}\n<\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    true\n<\/code><\/pre>\n\n\n\n
    Both unwanted values disappear.<\/p>\n\n\n\n
    \n\n\n\n
    18. Short Variable Declaration and _<\/code><\/h1>\n\n\n\n
    Consider:<\/p>\n\n\n\n
    value, err := getData()\n<\/code><\/pre>\n\n\n\n
    :=<\/code> creates variables.<\/p>\n\n\n\n
    But _<\/code> does not<\/strong> count as a newly declared variable.<\/p>\n\n\n\n
    For example:<\/p>\n\n\n\n
    _, err := getData()\n<\/code><\/pre>\n\n\n\n
    creates only:<\/p>\n\n\n\n
    err\n<\/code><\/pre>\n\n\n\n
    It does not create _<\/code>.<\/p>\n\n\n\n
    This becomes important when learning Go’s :=<\/code> rules later.<\/p>\n\n\n\n
    \n\n\n\n
    19. Common Patterns You Will See in Real Go Code<\/h1>\n\n\n\n
    Pattern 1 \u2014 Ignore slice index<\/h2>\n\n\n\n
    for _, user := range users {\n    fmt.Println(user)\n}\n<\/code><\/pre>\n\n\n\n
    Very common.<\/p>\n\n\n\n
    \n\n\n\n
    Pattern 2 \u2014 Map existence check<\/h2>\n\n\n\n
    if _, ok := users[\"Rajesh\"]; ok {\n    fmt.Println(\"User exists\")\n}\n<\/code><\/pre>\n\n\n\n
    Very common.<\/p>\n\n\n\n
    \n\n\n\n
    Pattern 3 \u2014 Ignore unwanted return value<\/h2>\n\n\n\n
    result, _ := calculate()\n<\/code><\/pre>\n\n\n\n
    Common, but be careful if the ignored value is an error.<\/p>\n\n\n\n
    \n\n\n\n
    Pattern 4 \u2014 Check type only<\/h2>\n\n\n\n
    if _, ok := data.(string); ok {\n    fmt.Println(\"It is a string\")\n}\n<\/code><\/pre>\n\n\n\n
    Common.<\/p>\n\n\n\n
    \n\n\n\n
    Pattern 5 \u2014 Side-effect import<\/h2>\n\n\n\n
    import _ \"some\/package\"\n<\/code><\/pre>\n\n\n\n
    More advanced.<\/p>\n\n\n\n
    \n\n\n\n
    Pattern 6 \u2014 Interface compile-time check<\/h2>\n\n\n\n
    var _ SomeInterface = (*SomeType)(nil)\n<\/code><\/pre>\n\n\n\n
    Very common in professional Go libraries.<\/p>\n\n\n\n
    \n\n\n\n
    20. When Should You NOT Use _<\/code>?<\/h1>\n\n\n\n
    The most important case is errors.<\/p>\n\n\n\n
    Avoid this unless you’re certain the error does not matter:<\/p>\n\n\n\n
    data, _ := os.ReadFile(\"config.txt\")\n<\/code><\/pre>\n\n\n\n
    If the file doesn’t exist, you’ve thrown away the explanation.<\/p>\n\n\n\n
    Better:<\/p>\n\n\n\n
    data, err := os.ReadFile(\"config.txt\")\n\nif err != nil {\n    fmt.Println(\"Unable to read file:\", err)\n    return\n}\n<\/code><\/pre>\n\n\n\n
    A good rule:<\/p>\n\n\n\n
    \n
    _<\/code> should mean \u201cI intentionally don’t need this value,\u201d<\/strong> not \u201cI don’t want to deal with this value.\u201d<\/strong><\/p>\n<\/blockquote>\n\n\n\n
    \n\n\n\n
    21. Quick Reference Table<\/h1>\n\n\n\n
    Situation<\/th>Example<\/th>Meaning<\/th><\/tr><\/thead>
    Ignore range index<\/td>for _, v := range x<\/code><\/td>Ignore index<\/td><\/tr>
    Ignore function result<\/td>x, _ := f()<\/code><\/td>Ignore second return<\/td><\/tr>
    Ignore map value<\/td>_, ok := m[k]<\/code><\/td>Only check key existence<\/td><\/tr>
    Ignore type assertion value<\/td>_, ok := x.(T)<\/code><\/td>Only check type<\/td><\/tr>
    Ignore parameter<\/td>func f(_ int)<\/code><\/td>Parameter intentionally unused<\/td><\/tr>
    Mark value unused<\/td>_ = x<\/code><\/td>Explicitly discard value<\/td><\/tr>
    Side-effect import<\/td>import _ \"pkg\"<\/code><\/td>Run package initialization only<\/td><\/tr>
    Interface check<\/td>var _ I = T{}<\/code><\/td>Verify interface implementation<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
    \n\n\n\n
    22. Beginner Mental Model<\/h1>\n\n\n\n
    Whenever you see:<\/p>\n\n\n\n
    _\n<\/code><\/pre>\n\n\n\n
    mentally replace it with:<\/p>\n\n\n\n
    IGNORE THIS VALUE\n<\/code><\/pre>\n\n\n\n
    So:<\/p>\n\n\n\n
    for _, item := range menu {\n<\/code><\/pre>\n\n\n\n
    becomes:<\/p>\n\n\n\n
    for IGNORE_INDEX, item := range menu\n<\/code><\/pre>\n\n\n\n
    And:<\/p>\n\n\n\n
    value, _ := function()\n<\/code><\/pre>\n\n\n\n
    becomes:<\/p>\n\n\n\n
    value, IGNORE_SECOND_RESULT := function()\n<\/code><\/pre>\n\n\n\n
    And:<\/p>\n\n\n\n
    _, ok := myMap[\"Rajesh\"]\n<\/code><\/pre>\n\n\n\n
    becomes:<\/p>\n\n\n\n
    IGNORE_VALUE, check_if_it_exists\n<\/code><\/pre>\n\n\n\n
    That mental model works for almost every beginner use of _<\/code>.<\/p>\n\n\n\n
    \n\n\n\n
    23. Mini Practice Program<\/h1>\n\n\n\n
    Try this complete program:<\/p>\n\n\n\n
    package main\n\nimport \"fmt\"\n\nfunc getUser() (string, int, string) {\n    return \"Rajesh\", 42, \"India\"\n}\n\nfunc main() {\n\n    \/\/ 1. Ignore slice index\n    languages := []string{\"Go\", \"Python\", \"Java\"}\n\n    for _, language := range languages {\n        fmt.Println(language)\n    }\n\n    \/\/ 2. Ignore second function result\n    name, _, country := getUser()\n\n    fmt.Println(name)\n    fmt.Println(country)\n\n    \/\/ 3. Ignore map value\n    users := map[string]int{\n        \"Rajesh\": 42,\n        \"John\":   35,\n    }\n\n    _, exists := users[\"Rajesh\"]\n\n    fmt.Println(\"Exists:\", exists)\n}\n<\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    Go\nPython\nJava\nRajesh\nIndia\nExists: true\n<\/code><\/pre>\n\n\n\n
    This one small program demonstrates three of the most important uses of the blank identifier.<\/p>\n\n\n\n
    \n\n\n\n
    24. Final Rule to Remember<\/h1>\n\n\n\n
    The entire concept can be summarized in one sentence:<\/p>\n\n\n\n
    _ = \"I intentionally don't need this value.\"\n<\/code><\/pre>\n\n\n\n
    For your current learning stage, master these three uses first<\/strong>:<\/p>\n\n\n\n
    \/\/ 1. range\nfor _, item := range items {\n}\n\n\/\/ 2. multiple return values\nvalue, _ := function()\n\n\/\/ 3. map existence\n_, ok := myMap[\"key\"]\n<\/code><\/pre>\n\n\n\n
    Once these feel natural, the advanced uses such as:<\/p>\n\n\n\n
    import _ \"package\"\n<\/code><\/pre>\n\n\n\n
    and:<\/p>\n\n\n\n
    var _ Interface = (*Type)(nil)\n<\/code><\/pre>\n\n\n\n
    will be much easier to understand.<\/p>\n","protected":false},"excerpt":{"rendered":"
    The underscore: is called the blank identifier in Go. The easiest way to understand it is: _ means: \u201cGo gives me this value, but I intentionally do… <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1047","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/posts\/1047","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/comments?post=1047"}],"version-history":[{"count":2,"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/posts\/1047\/revisions"}],"predecessor-version":[{"id":1051,"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/posts\/1047\/revisions\/1051"}],"wp:attachment":[{"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/media?parent=1047"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/categories?post=1047"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/tags?post=1047"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}