常見verbs
General
%v 變數的預設格式
%#v 使用go語法來表示這個值
%T 變數型別func main() {
s := []string{"a", "b", "c"}
fmt.Printf("%v\n", s) //["a", "b", "c"]
fmt.Printf("%#v\n", s) //[]string{"a", "b", "c"}
fmt.Printf("%T\n", s) //[]string
}Boolean
%t 變數的布林值t := true
fmt.Printf("%t\n", t) //trueInteger
%b base 2
%c the character represented by the corresponding Unicode code point
%d base 10
%o base 8
%O base 8 with 0o prefix
%q a single-quoted character literal safely escaped with Go syntax.
%x base 16, with lower-case letters for a-f
%X base 16, with upper-case letters for A-F 1 package main
2
3 import (
4 "fmt"
5 )
6
7 func main() {
8 n := 10
9 fmt.Printf("%b\n", n) //1010
10 fmt.Printf("%c\n", 97) //a
11 fmt.Printf("%d\n", 100) //100
12 fmt.Printf("%o\n", 8) //10
13 fmt.Printf("%O\n", 8) //0o10
14 fmt.Printf("%q\n", 97) //'a'
15 fmt.Printf("%x\n", 15) //f
16 fmt.Printf("%X\n", 15) //F
17 }Slice
%p address of 0th element in base 16 notation, with leading 0x 1 package main
2
3 import (
4 "fmt"
5 )
6
7 func main() {
8 s := []string{"cheng", "xiao", "shuo"}
9 fmt.Printf("%p\n", s) //0xc000054180
10 }預設格式%v
bool: %t
int, int8 etc.: %d
uint, uint8 etc.: %d, %#x if printed with %#v
float32, complex64, etc: %g
string: %s
chan: %p
pointer: %p複合型別列印的預設格式
struct: {field0 field1 ...}
array, slice: [elem0 elem1 ...]
maps: map[key1:value1 key2:value2 ...]
pointer to above: &{}, &[], &map[]Pointer
%p base 16 notation, with leading 0x
The %b, %d, %o, %x and %X verbs also work with pointers,
formatting the value exactly as if it were an integer. 1 package main
2
3 import (
4 "fmt"
5 )
6
7 func main() {
8 s := []int64{1,2,3}
9 fmt.Printf("%p\n", s)
10 fmt.Printf("%p\n", &s)
11 fmt.Printf("%b\n", s)
12 fmt.Printf("%b\n", &s)
13 fmt.Printf("%d\n", s)
14 fmt.Printf("%d\n", &s)
15 fmt.Printf("%o\n", s)
16 fmt.Printf("%o\n", &s)
17 }輸出：
0xc0000b6020
0xc0000a6020
[1 10 11]
&[1 10 11]
[1 2 3]
&[1 2 3]
[1 2 3]
&[1 2 3]###golang fmt pkg 中的例子：
package main
import (
"fmt"
"math"
"time"
)
func main() {
integer := 23
// Each of these prints "23" (without the quotes).
fmt.Println(integer)
fmt.Printf("%v\n", integer)
fmt.Printf("%d\n", integer)
// The special verb %T shows the type of an item rather than its value.
fmt.Printf("%T %T\n", integer, &integer)
// Result: int *int
// Booleans print as "true" or "false" with %v or %t.
truth := true
fmt.Printf("%v %t\n", truth, truth)
// Result: true true
answer := 42
fmt.Printf("%v %d %x %o %b\n", answer, answer, answer, answer, answer)
// Result: 42 42 2a 52 101010
pi := math.Pi
fmt.Printf("%v %g %.2f (%6.2f) %e\n", pi, pi, pi, pi, pi)
// Result: 3.141592653589793 3.141592653589793 3.14 ( 3.14) 3.141593e+00
point := 110.7 + 22.5i
fmt.Printf("%v %g %.2f %.2e\n", point, point, point, point)
// Result: (110.7+22.5i) (110.7+22.5i) (110.70+22.50i) (1.11e+02+2.25e+01i)
smile := '?'
fmt.Printf("%v %d %c %q %U %#U\n", smile, smile, smile, smile, smile, smile)
// Result: 128512 128512 ? '?' U+1F600 U+1F600 '?'
placeholders := `foo "bar"`
fmt.Printf("%v %s %q %#q\n", placeholders, placeholders, placeholders, placeholders)
// Result: foo "bar" foo "bar" "foo \"bar\"" `foo "bar"`
isLegume := map[string]bool{
"peanut": true,
"dachshund": false,
}
fmt.Printf("%v %#v\n", isLegume, isLegume)
// Result: map[dachshund:false peanut:true] map[string]bool{"dachshund":false, "peanut":true}
person := struct {
Name string
Age int
}{"Kim", 22}
fmt.Printf("%v %+v %#v\n", person, person, person)
// Result: {Kim 22} {Name:Kim Age:22} struct { Name string; Age int }{Name:"Kim", Age:22}
pointer := &person
fmt.Printf("%v %p\n", pointer, (*int)(nil))
// Result: &{Kim 22} 0x0
// fmt.Printf("%v %p\n", pointer, pointer)
// Result: &{Kim 22} 0x010203 // See comment above.
greats := [5]string{"Kitano", "Kobayashi", "Kurosawa", "Miyazaki", "Ozu"}
fmt.Printf("%v %q\n", greats, greats)
// Result: [Kitano Kobayashi Kurosawa Miyazaki Ozu] ["Kitano" "Kobayashi" "Kurosawa" "Miyazaki" "Ozu"]
kGreats := greats[:3]
fmt.Printf("%v %q %#v\n", kGreats, kGreats, kGreats)
// Result: [Kitano Kobayashi Kurosawa] ["Kitano" "Kobayashi" "Kurosawa"] []string{"Kitano", "Kobayashi", "Kurosawa"}
cmd := []byte("a⌘")
fmt.Printf("%v %d %s %q %x % x\n", cmd, cmd, cmd, cmd, cmd, cmd)
// Result: [97 226 140 152] [97 226 140 152] a⌘ "a⌘" 61e28c98 61 e2 8c 98
now := time.Unix(123456789, 0).UTC() // time.Time implements fmt.Stringer.
fmt.Printf("%v %q\n", now, now)
// Result: 1973-11-29 21:33:09 +0000 UTC "1973-11-29 21:33:09 +0000 UTC"
}例子
Errorf()
package main
import (
"fmt"
)
func main() {
const name, id = "bueller", 17
err := fmt.Errorf("user %q (id %d) not found", name, id)
fmt.Println(err.Error())
}Fprint()、Fprintf()、Fprintln()。輸出內容到io.writer
package main
import (
"fmt"
"os"
)
func main() {
const name, age = "Kim", 22
n, err := fmt.Fprint(os.Stdout, name, " is ", age, " years old.\n")
if err != nil {
fmt.Fprintf(os.Stderr, "Fprint: %v\n", err)
}
fmt.Print(n, " bytes written.\n")
n, err := fmt.Fprintf(os.Stdout, "%s is %d years old.\n", name, age)
if err != nil {
fmt.Fprintf(os.Stderr, "Fprintf: %v\n", err)
}
fmt.Printf("%d bytes written.\n", n)
n, err := fmt.Fprintln(os.Stdout, name, "is", age, "years old.")
if err != nil {
fmt.Fprintf(os.Stderr, "Fprintln: %v\n", err)
}
fmt.Println(n, "bytes written.")
}
Fscan()、Fscanf()、Fscanln()
package main
import (
"fmt"
"os"
"strings"
)
func main() {
var (
i int
b bool
s string
)
r := strings.NewReader("5 true gophers")
n, err := fmt.Fscanf(r, "%d %t %s", &i, &b, &s)
if err != nil {
fmt.Fprintf(os.Stderr, "Fscanf: %v\n", err)
}
fmt.Println(i, b, s)
fmt.Println(n)
s := `dmr 1771 1.61803398875
ken 271828 3.14159`
r := strings.NewReader(s)
var a string
var b int
var c float64
for {
n, err := fmt.Fscanln(r, &a, &b, &c)
if err == io.EOF {
break
}
if err != nil {
panic(err)
}
fmt.Printf("%d: %s, %d, %f\n", n, a, b, c)
}
}本作品採用《CC 協議》，轉載必須註明作者和本文連結