Go Package fmt: Difference between revisions

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{{Internal|Pointers_in_Go#Displaying_Pointers|Pointers in Go | Displaying Pointers}}
{{Internal|Pointers_in_Go#Displaying_Pointers|Pointers in Go | Displaying Pointers}}


===Structs===
==Structs==
{{Internal|Go_Structs#Printing_Structs|Go Structs | Printing Structs}}
{{Internal|Go_Structs#Printing_Structs|Go Structs | Printing Structs}}



Revision as of 21:58, 22 December 2023

External

Internal

Formatting

Conversion Characters

%v

Render the value as string in the default format.

%+v

When printing structs, the plus flag %+v adds field names.

%#v

A Go-syntax representation of the value.

%T

A Go-syntax representation of the type of the value.

%%

A literal percent sign. Consumes no value.

Strings

color := "blue"
fmt.Printf("The color is %s\n", color)

Integers

size := 1
fmt.Printf("The size is %d\n", size)

Characters

c := 'x'
fmt.Printf("The character is %c\n", c)

Booleans

b := true
fmt.Printf("The boolean value is %t\n", b)

Floating Point Numbers

f := 1.0
fmt.Printf("The floating point value is %f\n", f)

Pointers

Pointers in Go | Displaying Pointers

Structs

Go Structs | Printing Structs

Leading Zero Padding for Integers

i := 7
s := fmt.Sprintf("%06d", i) // will produce "000007" (five zeroes)

Leading Space Padding for Integer

i := 7
s := fmt.Sprintf("%6d", i) // will produce "     7" (five spaces)

Functions

Sprintf()

Format a string and returns it as a result:

message := fmt.Sprintf("Hi, %v. Welcome!", name)

For more details on the format string, see:

Printf() Format String

Printf(), Println()

Printing to stdout and stderr

Scanf(), Scanln()

Handling stdin in Go

Errorf()

Error Handling | Wrapping Errors

Interfaces

fmt.Stringer

type Stringer interface {
  String() string
}

Stringer is implemented by any type that has a String() method, which defines the "native" format for that value. The String() method is used to print values passed as an operand to any format that accepts a string or to an unformatted printer such as Print. For a usage example, see:

The Equivalent of Java toString() in Go