How to convert a string type value to a float type value in Go or Golang?

Published August 21, 2022

To convert a string type value to a float type value, you can use the ParseFloat() method from the strconv standard package in Go or Golang.

The ParseFloat() method:

  • accepts a string type value as its first argument
  • a bit size of int type value as its second argument
  • and returns 2 values, the first one being the converted float type value if any and the second being the error data if any.

TL;DR

package main

// import `strconv` package
import (
    "fmt"
    "strconv"
)

func main() {
    // convert `string` type value of "33.96"
    // using the `ParseFloat()` method and passing
    // the value "33.96" as its first argument
    // 64, the bit size as its second argument
    convertedFloatNum, err := strconv.ParseFloat("33.96", 64)
    // check if any error happened
    if err != nil {
        fmt.Println(err.Error())
        return
    }

    // log output of the `convertedFloatNum`
    // variable to the console
    fmt.Println(convertedFloatNum) // 33.96 and the type is float ✅
}

For example, let's say we need to convert a string type value of "33.96" to its corresponding float type value.

To do that let's first import the strconv standard package like this,

package main

// import `strconv` package
import "strconv"

After importing the package, inside the main() function we can use the ParseFloat() method from the strconv package and pass the string type value of "33.96" as its first argument, and 64 the bit size as its third argument to the function.

It can be done like this,

package main

// import `strconv` package
import "strconv"

func main(){
    // convert `string` type value of "33.96"
    // using the `ParseFloat()` method and passing
    // the value "33.96" as its first argument
    // 64, the bit size as its second argument
    strconv.ParseFloat("33.96", 64)
}

The ParseFloat() method returns 2 values where the first value is the converted float type value if successfully converted and the second value is the error data if anything happened during the conversion. To capture these 2 data, let's assign 2 variables.

It can be done like this,

package main

// import `strconv` package
import "strconv"

func main(){
    // convert `string` type value of "33.96"
    // using the `ParseFloat()` method and passing
    // the value "33.96" as its first argument
    // 64, the bit size as its second argument
    convertedFloatNum, err := strconv.ParseFloat("33.96", 64)
}

Before dealing with the converted float value we need to check if there was any error during the conversion process. Let's use a simple if conditional statement and check to see if the err data variable is nil or not. If it is not nil, then there must have been an error that happened during the conversion.

It can be done like this,

package main

// import `strconv` package
import (
    "fmt"
    "strconv"
)

func main(){
    // convert `string` type value of "33.96"
    // using the `ParseFloat()` method and passing
    // the value "33.96" as its first argument
    // 64, the bit size as its second argument
    convertedFloatNum, err := strconv.ParseFloat("33.96", 64)
    // check if any error happened
    if err != nil {
        fmt.Println(err.Error())
        return
    }
}

If there is no error then it is safe to assume that the convertedFloatNum variable must be having the converted float type value. Let's log the output to the console like this,

package main

// import `strconv` package
import (
    "fmt"
    "strconv"
)

func main() {
    // convert `string` type value of "33.96"
    // using the `ParseFloat()` method and passing
    // the value "33.96" as its first argument
    // 64, the bit size as its second argument
    convertedFloatNum, err := strconv.ParseFloat("33.96", 64)
    // check if any error happened
    if err != nil {
        fmt.Println(err.Error())
        return
    }

    // log output of the `convertedFloatNum`
    // variable to the console
    fmt.Println(convertedFloatNum) // 33.96 and the type is float ✅
}

As you can see that the string type value of "33.96" is successfully converted to its corresponding float type value which is what we want.

See the above code live in The Go Playground.

Now let's try to give a string type value composed of alphabets like John Doe and then try to convert it to its float type value like this,

package main

// import `strconv` package
import (
    "fmt"
    "strconv"
)

func main() {
    // convert `string` type value of "John Doe"
    // using the `ParseFloat()` method and passing
    // the value "John Doe" as its first argument
    // 64, the bit size as its third argument
    convertedFloatNum, err := strconv.ParseFloat("John Doe", 64) // Error ❌. strconv.ParseFloat: parsing "John Doe": invalid syntax
    // check if any error happened
    if err != nil {
        fmt.Println(err.Error())
        return
    }

    // log output of the `convertedFloatNum`
    // variable to the console
    fmt.Println(convertedFloatNum)
}

As you can see that the Go compiler shows us an error saying that strconv.ParseFloat: parsing "John Doe": invalid syntax which essentially means that it cannot parse this value to its corresponding float type value.

See the above code live in The Go Playground.

That's all 😃!

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