How to Use strconv Package in Go: Convert Strings and Numbers Easily

The strconv package in Go provides functions to convert strings to basic data types like integers and floats, and to convert these types back to strings. Use functions like strconv.Atoi to convert a string to an integer, and strconv.Itoa to convert an integer to a string.

Syntax

The strconv package offers functions for conversions between strings and basic types.

• strconv.Atoi(string) (int, error): Converts a string to an integer.
• strconv.Itoa(int) string: Converts an integer to a string.
• strconv.ParseBool(string) (bool, error): Converts a string to a boolean.
• strconv.FormatBool(bool) string: Converts a boolean to a string.
• strconv.ParseFloat(string, bitSize int) (float64, error): Converts a string to a float64 or float32.
• strconv.FormatFloat(float64, fmt byte, prec int, bitSize int) string: Converts a float to a string.

go

package main

import (
	"fmt"
	"strconv"
)

func main() {
	// Convert string to int
	i, err := strconv.Atoi("123")
	if err != nil {
		fmt.Println("Error:", err)
	}
	fmt.Println("Integer:", i)

	// Convert int to string
	s := strconv.Itoa(456)
	fmt.Println("String:", s)
}

Output

Integer: 123
String: 456

Example

This example shows how to convert strings to integers and booleans, and back to strings using strconv. It also handles errors when conversion fails.

go

package main

import (
	"fmt"
	"strconv"
)

func main() {
	// String to int
	numStr := "42"
	num, err := strconv.Atoi(numStr)
	if err != nil {
		fmt.Println("Conversion error:", err)
	} else {
		fmt.Println("Converted integer:", num)
	}

	// Int to string
	str := strconv.Itoa(100)
	fmt.Println("Converted string:", str)

	// String to bool
	boolStr := "true"
	b, err := strconv.ParseBool(boolStr)
	if err != nil {
		fmt.Println("Bool conversion error:", err)
	} else {
		fmt.Println("Converted bool:", b)
	}

	// Bool to string
	boolToStr := strconv.FormatBool(false)
	fmt.Println("Bool to string:", boolToStr)
}

Output

Converted integer: 42
Converted string: 100
Converted bool: true
Bool to string: false

Common Pitfalls

Common mistakes when using strconv include:

• Ignoring errors returned by conversion functions, which can cause unexpected behavior.
• Using strconv.Atoi on strings that are not valid integers, leading to errors.
• Confusing strconv.Itoa (int to string) with strconv.Atoi (string to int).
• Not specifying the correct bit size when parsing floats with strconv.ParseFloat.

go

package main

import (
	"fmt"
	"strconv"
)

func main() {
	// Wrong: ignoring error
	num, _ := strconv.Atoi("abc") // "abc" is not a number
	fmt.Println("Number:", num) // Prints 0 silently

	// Right: check error
	num2, err := strconv.Atoi("abc")
	if err != nil {
		fmt.Println("Error detected:", err)
	} else {
		fmt.Println("Number:", num2)
	}
}

Output

Number: 0
Error detected: strconv.Atoi: parsing "abc": invalid syntax

Quick Reference

Function	Description	Example
strconv.Atoi(string)	Convert string to int	i, err := strconv.Atoi("123")
strconv.Itoa(int)	Convert int to string	s := strconv.Itoa(123)
strconv.ParseBool(string)	Convert string to bool	b, err := strconv.ParseBool("true")
strconv.FormatBool(bool)	Convert bool to string	s := strconv.FormatBool(true)
strconv.ParseFloat(string, bitSize int)	Convert string to float64 or float32	f, err := strconv.ParseFloat("3.14", 64)
strconv.FormatFloat(float64, fmt byte, prec int, bitSize int)	Convert float to string	s := strconv.FormatFloat(3.14, 'f', 2, 64)

Key Takeaways

Always check errors returned by strconv conversion functions to avoid silent failures.

Use strconv.Atoi and strconv.Itoa for converting between strings and integers.

Use strconv.ParseBool and strconv.FormatBool for boolean conversions.

For floats, use strconv.ParseFloat and strconv.FormatFloat with correct bit sizes.

The strconv package is essential for safe and easy string and number conversions in Go.