catalogue

variable

statement

initialization

General form

Type derivation

Omit var

use

Anonymous variable

Scope

global variable

local variable

constant

All codes

screenshot

reference resources

variable

The Go language variable name consists of letters, numbers and underscores. The first character cannot be a number. Use the var keyword.

statement

var variable name 1 [, variable name 2...] type

Note: one or more variables can be declared, and the declared value is zero

Zero value: 0, "", false, nil, etc

code

var num int
var num1,num2 int

initialization

General form

var variable name 1 [, variable name 2...] [type] = value1[,value2...]

Note: after initialization, it must also be used later. The type can be determined automatically without writing

Code

var num3 int8 = 1

Type derivation

It doesn't write type on it

var variable name 1 [, variable name 2...]= value1[,value2...]

Note: integer defaults to int and floating point defaults to float64

Code

var num4 = 2

Omit var

Variable name 1 [, variable name 2...]:= value1[,value2...]

I personally recommend this, similar to Python, without writing variable types.

Code

f1 := 5.0

There is another form, which is often used for global variable declarations

var (

Variable 1 = value1

Variable 2 = value2

)

code

var (
	author = "lady_killer9"
	time = "now"
)

use

Output, assignment and calculation are OK, and the exchange is simple

num1 = 1
num2 = 2
num1,num2 = num2,num1

Anonymous variable

_， Underline

This receiver can be used when the data is no longer used

all,_ := sumDiffer(num1,num2)

Scope

Note: variable names cannot be the same in the same scope

global variable

Function, lowercase package, uppercase cross package

Note: the form of omitting var cannot be used

//Global: = 1 error: Global unexpected
var Global = 1

local variable

In function, in for/if

code

func sumDiffer(a int,b int) (int,int) {
	return a+b,a-b
}

fmt.Println("author time:",author,time)
//fmt.Println(a,b) a,b are local variables in sumdifference function and cannot be accessed

constant

A constant is an identifier of a simple value that will not be modified when the program runs.

The data types in constants can only be Boolean, numeric (integer, floating point and complex) and string.

Use the keyword const

const variable name [type] = value

const Pi = 3.1415926

All codes

package main
import "fmt"
var (
	author = "lady_killer9"
	time = "now"
)
//Global: = 1 error: Global unexpected
var Global = 1
func sumDiffer(a int,b int) (int,int) {
	return a+b,a-b
}
func main() {
	//-------------Statement--------------
	// Declare a single variable, num = 0
	var num int
	// Declare multiple variables, num1 and num2 are 0
	var num1,num2 int
	fmt.Println("num:",num)
	fmt.Println("num1 num2:",num1,num2)

	//-----------Initialize---------------
	// Common form
	var num3 int8 = 1
	//Type derivation
	var num4 = 2
	// Omit var
	f1 := 5.0
	fmt.Printf("num3:%v,num4 Type of:%T,num4:%v,f1 Type of:%T,f1:%v\n",num3,num4,num4,f1,f1)

	//-----------Variable use-----------
	num1 = 1
	num2 = 2
	num1,num2 = num2,num1
	fmt.Println("num1 num2:",num1,num2)

	//------------Anonymous variable----------
	all,_ := sumDiffer(num1,num2)
	fmt.Println("num1+num2:",all)

	//-----------Scope----------
	fmt.Println("author time:",author,time)
	fmt.Println("Global:",Global)
	//fmt.Println(a,b) a,b are local variables in sumdifference function and cannot be accessed

	//-----------Constant------------
	const Pi = 3.1415926
	fmt.Println("Pi:",Pi)
}

screenshot

reference resources

Go declaration syntax

Go Guide

More Go related content: ***

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