How to replace placeholders in go language

Method for placeholder replacement in go language: 1. Use the syntax "func Printf(format string, args...interface{})" to output strings and integers; 2. Use "func Sprintf(format string, args ...interface{})" to format the string; 3. Take out the value represented by the placeholder and replace it with a new string; 4. Use the "Println" function to output the result to the console .

#The operating environment of this article: Windows 10 system, go1.20 version, dell g3 computer.

In the Go language, placeholders refer to special characters used for formatted output. The placeholder is represented by the % character in the string, followed by a specific format specifier to specify the data type and format to be output. There are many kinds of placeholders in Go language, including %s, %d, %f, etc.

When using placeholders, we need to pass the placeholder and the actual value to be output to the formatted output function. In Go language, we can use the Printf function in the fmt package to format output. The syntax of this function is as follows:

func Printf(format string, args ...interface{}) (n int, err error)

Among them, the format parameter is a string that contains the content to be output and placeholders. The args parameter is a variable parameter list used to pass the actual value to be output. Its number and order must match the number and order of placeholders.

For example, we can use the following code to output a string and an integer:

package main
import "fmt"
func main() {
name := "John"
age := 30
fmt.Printf("My name is %s and I am %d years old.", name, age)
}

In this example, %s means to output a string, and %d means to output an integer . The first parameter of the Printf function is a string containing two placeholders, and the second parameter is a variable parameter list containing the actual value to be output, where the first value is a string, and the second parameter is a variable parameter list containing the actual value to be output. The second value is an integer.

Sometimes, we need to replace one or more placeholders in a string instead of replacing all placeholders. In this case, we can use the Sprintf function to format the output first, then convert the result into a string, and operate on the string. The syntax of the Sprintf function is as follows:

func Sprintf(format string, args ...interface{}) string

For example, we can use the following code to replace the first placeholder in the string:

package main
import "fmt"
func main() {
name := "John"
age := 30
str := fmt.Sprintf("My name is %s and I am %d years old.", name, age)
newStr := "Jack"
str = fmt.Sprintf("%s%s", newStr, str[4:])
fmt.Println(str)
}

In this example, we first use Sprintf The function formats the output of the string and obtains a new string. Then, we take the value represented by the first placeholder in the string and replace it with a new string. Finally, we use the Println function from the fmt package to output the results to the console.

It should be noted that since strings are immutable, when replacing a placeholder in a string, we must use a method similar to the above code to first convert the string into a character. section array or rune array, then perform operations, and finally convert it into a string output.

In short, in Go language, it is very convenient and commonly used to use placeholders for formatted output. By using placeholders, we can easily output various types of data to the console or file, and we can freely replace and modify the placeholders in the string

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