Golang: Print

By Xah Lee. Date: . Last updated: .

Format and Print: fmt.Printf

Use the package fmt

fmt.Printf("there are %v apples\n", 3)

The first argument is a string. The string can contain many special placeholder characters , starting with the percent character % (U+25: PERCENT SIGN)

2nd argument and rest arguments are used to fill the placeholders.

example:

fmt.Printf("Name is %v, Age is %v \n", "john", 36)

package main

import "fmt"

func main() {

	var x = "John"
	var y = 36

	fmt.Printf("name is %v, age is %v\n", x, y)
	// name is John, age is 36

}

Here's the most useful placeholders:

Print Line: fmt.Println

For quick printing, use

fmt.Println(v1, v2 etc)

it's similar to fmt.Printf with "%v" for format.

package main

import "fmt"

func main() {

	var x = 3
	var y = 4
	fmt.Println(x, y) // 3 4
}

Format to String

To convert a value to string, use

fmt.Sprintf(string, v1, v2 etc)

it return a string instead of printing.

package main

import "fmt"

func main() {

	var x = "John"
	var y = 36

	var s = fmt.Sprintf("name is %v, age is %v\n", x, y)

	fmt.Println(s == "name is John, age is 36\n") // true
}

Example: Print Type

It is very useful to print the type of a value, when learning go.

fmt.Printf("%T\n", val)

package main

import "fmt"

// using Printf to show different types of value

func main() {

	var x = 3
	fmt.Printf("%v\n", x) // 3
	fmt.Printf("%T\n", x) // int

	var x2 = 3.4
	fmt.Printf("%v\n", x2) // 3.4
	fmt.Printf("%T\n", x2) // float64

}

Example: Print String

Golang: Print String

Example: Print Slice

Golang: Slice

Example: Print Struct

Golang: Struct

Print String, as Bytes, Character, Codepoint

see Golang: String

Reference

https://golang.org/pkg/fmt/

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Golang

  1. Compile, Run
  2. Source Encoding
  3. Package, Import
  4. Comment
  5. Print
  6. String
  7. String Functions
  8. Print String
  9. String Backslash Escape
  10. Rune
  11. Variable
  12. Zero Value
  13. Constant
  14. If Then Else
  15. Switch/Case
  16. Loop
  17. Basic Types
  18. Array
  19. Slice
  20. Map
  21. Struct
  22. Function
  23. Closure
  24. Pointer
  25. String, Byte Slice, Rune Slice
  26. regexp
  27. Read File
  28. Write to File
  29. Walk Dir
  30. Check File Exist
  31. System Call
  32. Get Script Path
  33. Defer
  34. Random Number

Examples

  1. Match Any Regexp
  2. Find String
  3. Find Replace
  4. Validate Links
  5. Generate Sitemap

Reference

  1. Go Spec