How to Best Format Floating Point Numbers as Strings in Go?

Best Practices for Formatting Floating Point Numbers as Strings in Go

When working with floating point numbers in Go, it is often necessary to convert them into strings for displaying or processing. This task can be accomplished using a variety of approaches, each with its own advantages and disadvantages.

fmt.Sprintf

fmt.Sprintf is a convenient function for formatting a floating point number into a string. It uses the format specifier %.2f to control the number of decimal places:

var sResult1 string = fmt.Sprintf("%.2f", fResult)

strconv.FormatFloat

strconv.FormatFloat offers more flexibility than fmt.Sprintf for controlling the formatting of the string. It accepts various parameters, including the bit size (32 or 64) of the floating point value:

var sResult2 string = strconv.FormatFloat(float64(fResult), 'f', 2, 32)

Recommendation

For cases where the precision of the formatted string is fixed, either fmt.Sprintf or strconv.FormatFloat can be used, and they will produce equivalent results. However, if the precision is variable, strconv.FormatFloat is more convenient to use.

Bit Size Explanation

The final argument to strconv.FormatFloat controls how the value is rounded. According to the documentation, it assumes the original value was obtained from a floating-point value of the specified bit size (32 for float32, 64 for float64).

Hence, when working with float32 values, as in the example provided, passing 32 is correct.

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