Use the strconv.FormatFloat function to convert a floating point number to a string and set the precision and format

Use the strconv.FormatFloat function to convert floating point numbers into strings, and set the precision and format.

In the Go language, we often need to convert floating point numbers into strings. In this process, we often need Control precision and format. The strconv package of Go language provides a FormatFloat function that can help us complete this task.

The FormatFloat function has three parameters, which are the floating point number to be converted, the format flag and the precision. Format tags are used to specify the format in which the converted string should be displayed. The argument used to specify precision determines how many decimal places the converted string should retain.

The following is a simple sample code:

package main

import (
    "fmt"
    "strconv"
)

func main() {
    f := 3.14159

    // 转换为字符串，默认保留小数点后6位
    str1 := strconv.FormatFloat(f, 'f', -1, 64)
    fmt.Println(str1) // 输出：3.141590

    // 保留两位小数
    str2 := strconv.FormatFloat(f, 'f', 2, 64)
    fmt.Println(str2) // 输出：3.14

    // 科学计数法
    str3 := strconv.FormatFloat(f, 'e', -1, 64)
    fmt.Println(str3) // 输出：3.141590e+00
}

In the above code, we define a floating point number f with a value of 3.14159. Then use the FormatFloat function to convert f to a string.

In the first example, we use the default format tag 'f' and set the precision to -1. In this case, the FormatFloat function determines the number of decimal places to retain based on the number of decimal places in f. Since f has 5 decimal places, the final string is "3.141590".

In the second example, we kept two decimal places. To do this we set the format flag to 'f' and then set the precision to 2. So the final string is "3.14".

In the third example, we used scientific notation to represent floating point numbers. We set the format flag to 'e' and then set the precision to -1. So the final string is "3.141590e 00".

When using the FormatFloat function, we need to pay attention to the following points:

• The format mark can be a lowercase letter 'f', 'e' or 'g', or it can be an uppercase letter The letters 'F', 'E' or 'G'. Among them, 'f' represents the decimal form, 'e' represents the scientific notation form, and 'g' represents the general format.
• The precision parameter can be a positive integer, indicating the number of decimal places to be retained; it can also be -1, indicating that the number of retained digits is automatically determined based on the number of decimal places in the floating point number.
• The third parameter of the FormatFloat function indicates conversion in the format of 64-bit floating point numbers. Normally, we use 64-bit floating point numbers to meet our needs.

To summarize, the FormatFloat function in the strconv package of Go language can easily convert floating point numbers to strings, and the precision and format can be set as needed. This function is very practical in the process of string conversion of floating point numbers and can help us meet the needs of various scenarios.

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