In Go, why does printing strings with Println and string() functions have different effects?

Go language string printing: Detailed explanation of the behavioral differences between Println and string() functions

There are many ways to print strings in Go language, and Println and string() functions are two of the commonly used methods. However, when they process non-string type variables, their output results are very different. This article will explore this difference in depth and provide the correct approach.

When printing a variable directly using the Println function, Go will automatically convert the variable to its string representation. For example:

num := 12345
fmt.Println(num) // Output: 12345

This code correctly prints the value of the integer num . However, if you use the string() function, the result is very different:

fmt.Println(string(num)) // The output may be an invisible character or garbled code

This is because string() function interprets the integer num as a Unicode code point and tries to convert it to the corresponding UTF-8 characters. For some integers, such as negative numbers or numbers outside the range of valid Unicode, string() function returns an invalid Unicode character (usually displayed as "\uffffd"), causing it to fail to print properly.

Therefore, string() function is not suitable for converting integers into strings directly. The correct way to do this is to use the Itoa function in strconv package:

import "strconv"

num := 12345
fmt.Println(strconv.Itoa(num)) // Output: 12345

The strconv.Itoa function is specifically used to convert integers into their string representations, thus avoiding possible errors from string() function.

Summary: In Go language, when printing integer variables, you should directly use Println or strconv.Itoa function to convert. Do not directly use string() function to avoid unexpected results. string() function is mainly used to process real strings or byte arrays and convert them to string types.

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