Go Formatting Verbs

Formatting Verbs for Printf()

• Go provides a variety of formatting verbs that can be used with the Printf() function to format and display output in a structured way. These verbs control how different types of data are printed.

General Formatting Verbs in Go

• These formatting verbs can be used with any data type in Go:

Verb         Description

%v            Displays the value using the default format

%#v       Displays the value in Go syntax format

%T            Prints the data type of the value

%%            Prints a literal percent sign (%)

Example:

package main

import "fmt"

func main() {

  number := 15.5

  message := "Hello World!"

  fmt.Printf("Default format: %v\n", number)

  fmt.Printf("Go-syntax format: %#v\n", number)

  fmt.Printf("With percentage: %v%%\n", number)

  fmt.Printf("Type of number: %T\n", number)

  fmt.Printf("Default format: %v\n", message)

  fmt.Printf("Go-syntax format: %#v\n", message)

  fmt.Printf("Type of message: %T\n", message)

}

Output:

Default format: 15.5

Go-syntax format: 15.5

With percentage: 15.5%

Type of number: float64

Default format: Hello World!

Go-syntax format: "Hello World!"

Type of message: string

Integer Formatting Verbs in Go

• The following formatting verbs are used with the Printf() function to format integer values in various ways:

Verb               Description

%b                  Binary (base 2)

%d                 Decimal (base 10)

%+d         Decimal with sign (always show sign)

%o                 Octal (base 8)

%O           Octal with leading 0o

%x                 Hexadecimal (base 16, lowercase)

%X                 Hexadecimal (base 16, uppercase)

%#x                Hexadecimal with leading 0x

%4d                Decimal, width 4 (right-aligned, padded with spaces)

%-4d        Decimal, width 4 (left-aligned, padded with spaces)

%04d        Decimal, width 4 (padded with leading zeros)

Example:

package main

import "fmt"

func main() {

var i = 15

fmt.Printf("Binary       : %b\n", i)

fmt.Printf("Decimal      : %d\n", i)

fmt.Printf("Signed       : %+d\n", i)

fmt.Printf("Octal        : %o\n", i)

fmt.Printf("Octal (0o)   : %O\n", i)

fmt.Printf("Hex (lower)  : %x\n", i)

fmt.Printf("Hex (upper)  : %X\n", i)

fmt.Printf("Hex (0x)     : %#x\n", i)

fmt.Printf("Width 4      : %4d\n", i)

fmt.Printf("Left Align   : %-4d\n", i)

fmt.Printf("Zero Padded  : %04d\n", i)

}

Output:

Binary       : 1111  

Decimal      : 15    

Signed       : +15   

Octal        : 17    

Octal (0o)   : 0o17  

Hex (lower)  : f     

Hex (upper)  : F     

Hex (0x)     : 0xf   

Width 4      :   15  

Left Align   : 15    

Zero Padded  : 0015  

String Formatting Verbs in Go

• The Printf() function in Go supports various formatting verbs for working with string values. Below are commonly used verbs for string formatting:

Verb Description

%s         Prints the value as a plain string

%q         Prints the value as a double-quoted string

%8s    Prints the string right-justified with width 8

%-8s Prints the string left-justified with width 8

%x          Prints the string as a hexadecimal dump of byte values

% x         Prints the hex dump with spaces between byte values

Example:

package main

import ("fmt")

func main() {

  var txt = "Hello"

  fmt.Printf("%s\n", txt)

  fmt.Printf("%q\n", txt)

  fmt.Printf("%8s\n", txt)

  fmt.Printf("%-8s\n", txt)

  fmt.Printf("%x\n", txt)

  fmt.Printf("% x\n", txt)

}

Output:

Hello

"Hello"

   Hello

Hello   

48656c6c6f

48 65 6c 6c 6f

Boolean Formatting Verbs

• In Go, the following formatting verb is used with boolean data types:

Verb Description

%t        Prints the boolean value as true or false (equivalent to %v)

Example:

package main

import (

  "fmt"

)

func main() {

  var i = true

  var j = false

  fmt.Printf("%t\n", i)

  fmt.Printf("%t\n", j)

}

Output:

true

false

Float Formatting Verbs

• The following formatting verbs can be used with float data types in Go:

Verb Description

%e         Scientific notation with e as the exponent

%f         Decimal format without exponent

%.2f Decimal with 2 digits after the decimal point

%6.2f Width 6, right-aligned, with 2 decimal places

%g         Compact format: uses %e or %f as needed

Example

package main

import ("fmt")

func main() {

  var i = 3.141

  fmt.Printf("%e\n", i)     // scientific notation

  fmt.Printf("%f\n", i)     // full decimal

  fmt.Printf("%.2f\n", i)   // 2 decimal places

  fmt.Printf("%6.2f\n", i)  // width 6, 2 decimals

  fmt.Printf("%g\n", i)     // compact representation

}

Output:

3.141000e+00

3.141000

3.14

  3.14

3.141