为什么Go中的fmt.Println打印动词％s文字而不是值？

Question

Consider,

package main
import "fmt"

func main() {
  name := "johnny"
  fmt.Println("Hello world %s
", name)
}

prints out,

Hello world %s johnny

---

Why do I get the %s instead of this,

package main
import "fmt"

func main() {
  name := "johnny"
  fmt.Printf("Hello world %s
", name)
}

which prints Hello world johnny?

I have tried to figure out the answer from the documentation,

If the format (which is implicitly %v for Println etc.) is valid for a string (%s %q %v %x %X), the following two rules apply:

1. If an operand implements the error interface, the Error method will be invoked to convert the object to a string, which will then be formatted as required by the verb (if any).

2. If an operand implements method String() string, that method will be invoked to convert the object to a string, which will then be formatted as required by the verb (if any).

But I'm having trouble understanding if this is affecting my program.

Answer 1

the f in Printf is for "Formatting." That's why the %? verbs do anything at all, because the function is built to parse for them. Println does no such formatting.

Formatting isn't a property of strings like in some languages (maybe you, like myself, came from Python?)