How to convert float to string

Question

I read a float from a file and will have to convert it to string. My problem here is that I am unsure of how many digits will be there after the decimal. I need to take the float exactly and convert it to string.

For ex: 
1.10 should be converted to "1.10"
Also,
1.5 should be converted to "1.5"
Can someone suggest how to go about this?

Possible duplicate of [How to format floating point numbers into a string using Go](https://stackoverflow.com/questions/18951359/how-to-format-floating-point-numbers-into-a-string-using-go) — nilsocket, Nov 15 '18 at 06:05

Ullaakut · Answer 1 · 2023-08-24T11:15:22.573

20

Use strconv.FormatFloat like such:

s := strconv.FormatFloat(3.1415, 'f', -1, 64)
fmt.Println(s)

Outputs

3.1415

edited Aug 24 '23 at 11:15

answered Nov 15 '18 at 05:28

Ullaakut

3,554
2
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Wrong, this outputs `3.1415E+00` (https://go.dev/play/p/-l7YeX1bzAL). use `strconv.FormatFloat(3.1415, 'f', -1, 64)` instead to have `3.1415` (https://go.dev/play/p/sSThokQeavt) – Yanis.F Jul 27 '23 at 04:10
Indeed, thanks for the correction @Yanis.F, it is corrected now. – Ullaakut Aug 24 '23 at 11:15

ASHWIN RAJEEV · Answer 2 · 2018-11-16T09:01:37.530

11

Convert float to string

FormatFloat converts the floating-point number f to a string, according to the format fmt and precision prec. It rounds the result assuming that the original was obtained from a floating-point value of bitSize bits (32 for float32, 64 for float64).

func FormatFloat(f float64, fmt byte, prec, bitSize int) string

f := 3.14159265
s := strconv.FormatFloat(f, 'E', -1, 64)
fmt.Println(s)

Output is "3.14159265"

Another method is by using fmt.Sprintf

s := fmt.Sprintf("%f", 123.456) 
fmt.Println(s)

Output is "123.456000"

Check the code on play ground

edited Nov 16 '18 at 09:01

answered Nov 15 '18 at 07:23

ASHWIN RAJEEV

2,525
1
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1

What is the fastest way? I guess that the FormatFloat() works faster – Sergey Ponomarev Dec 03 '21 at 17:27
2

Indeed, `FormatFloat` is faster and makes less allocations. – Ullaakut Dec 14 '21 at 07:32

score 7 · Answer 3 · edited May 20 '20 at 00:38

7

func main() {
    var x float32
    var y string
    x= 10.5
    y = fmt.Sprint(x)
    fmt.Println(y)
}

edited May 20 '20 at 00:38

pretzelhammer

13,874
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98

answered May 19 '20 at 11:16

Ayush Rastogi

71
1
4

Be careful when using `fmt.Sprint` and other similar functions, as they are slower and make more allocations than using `strconv` functions. – Ullaakut Dec 14 '21 at 07:33

score 1 · Answer 4 · answered Jul 27 '23 at 13:54

Depending on the size of your float number choose most suitable option:

var (
    floatNumber float64 = 27.156633168032640
)

fmt.Println("as float32 with 'E' (decimal exponent) :", strconv.FormatFloat(floatNumber, 'E', -1, 32))
fmt.Println("as float64 with 'E' (decimal exponent) :", strconv.FormatFloat(floatNumber, 'E', -1, 64))
fmt.Println("as float32 with 'f' (no exponent) :", strconv.FormatFloat(floatNumber, 'f', -1, 32))
fmt.Println("as float64 with 'f' (no exponent) :", strconv.FormatFloat(floatNumber, 'f', -1, 64))
fmt.Println("with fmt.Sprint :", fmt.Sprint(floatNumber))
fmt.Println("with fmt.Sprintf :", fmt.Sprintf("%f", floatNumber))

The result is:

P.S. for better performance you should use strconv.FormatFloat()

How to convert float to string

4 Answers4

Convert float to string