Golang strconv.FormatFloat Function

The strconv.FormatFloat function in Golang is part of the strconv package and is used to convert a floating-point number into its string representation. This function is particularly useful when you need to format floating-point numbers as strings for output, logging, or data serialization.

Table of Contents

1. Introduction
2. strconv.FormatFloat Function Syntax
3. Examples
   • Basic Usage
   • Formatting with Different Precision Levels
   • Converting and Formatting Float Values
4. Real-World Use Case Example
5. Conclusion

Introduction

The strconv.FormatFloat function provides a way to convert floating-point numbers (float32 or float64) into a string representation, with control over the formatting style and precision. This function is commonly used when floating-point numbers need to be displayed, stored as strings, or sent over a network in textual form.

strconv.FormatFloat Function Syntax

The syntax for the strconv.FormatFloat function is as follows:

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

Parameters:

• f float64: The floating-point number to be formatted.
• fmt byte: The format specifier for the floating-point representation ('b', 'e', 'E', 'f', 'g', 'G').
• prec int: The precision of the formatted output.
• bitSize int: The size (32 for float32 or 64 for float64) of the floating-point number.

Returns:

• string: The string representation of the floating-point number.

Behavior:

• Formats the floating-point number: The function converts the floating-point number into a string, formatting it according to the specified format, precision, and bit size.

Examples

Basic Usage

This example demonstrates how to use strconv.FormatFloat to convert a floating-point number into its string representation.

Example

package main

import (
	"fmt"
	"strconv"
)

func main() {
	f := 3.14159
	str := strconv.FormatFloat(f, 'f', 2, 64)
	fmt.Println("Formatted float:", str)
}

Output:

Formatted float: 3.14

Explanation:

• The strconv.FormatFloat function converts the floating-point number 3.14159 into the string "3.14" with a precision of two decimal places.

Formatting with Different Precision Levels

This example shows how to use strconv.FormatFloat to format floating-point numbers with varying levels of precision.

Example

package main

import (
	"fmt"
	"strconv"
)

func main() {
	f := 123.456789
	str1 := strconv.FormatFloat(f, 'f', 2, 64)
	str2 := strconv.FormatFloat(f, 'f', 5, 64)

	fmt.Println("Precision 2:", str1)
	fmt.Println("Precision 5:", str2)
}

Output:

Precision 2: 123.46
Precision 5: 123.45679

Explanation:

• The strconv.FormatFloat function is used to format the same floating-point number with different precisions, showing how the output changes based on the precision specified.

Converting and Formatting Float Values

This example demonstrates how to use strconv.FormatFloat in a more complex scenario where you convert a float value and format it for output.

Example

package main

import (
	"fmt"
	"strconv"
)

func main() {
	rawValue := 9876.54321
	roundedValue := strconv.FormatFloat(rawValue, 'g', 4, 64)

	fmt.Println("Rounded value:", roundedValue)
}

Output:

Rounded value: 9.877e+03

Explanation:

• The strconv.FormatFloat function converts and formats the floating-point number 9876.54321 using the general format ('g') with a precision of 4, which results in a scientific notation.

Real-World Use Case Example: Generating a Report

A practical use case for strconv.FormatFloat is generating a report where floating-point numbers need to be displayed with specific formatting.

Example: Generating a Financial Report

package main

import (
	"fmt"
	"strconv"
)

func main() {
	amount := 123456.789
	report := "Total Amount: $" + strconv.FormatFloat(amount, 'f', 2, 64)
	fmt.Println(report)
}

Output:

Total Amount: $123456.79

Explanation:

• The strconv.FormatFloat function is used to format the amount with two decimal places, making it suitable for financial reporting.

Conclusion

The strconv.FormatFloat function in Go is used for converting and formatting floating-point numbers into strings. It provides precise control over how numbers are represented, making it useful in a wide range of applications, from simple output formatting to complex data serialization. Whether you’re generating reports, logging data, or preparing numbers for display, strconv.FormatFloat ensures that your floating-point values are correctly formatted in your Go applications.