print#
fmt.Printf
- Printf is an abbreviation for "print formatted"
- Printf is used to create formatted output
- Printf does not automatically add a newline character, so you need to add \n or other characters yourself to control line breaks.
- Printf needs to use placeholders (such as %s, %d, %f, etc.) to specify the format of the output text and provide the corresponding values.
Println
- Println is an abbreviation for "print line"
- It is used to print text and add a newline character at the end, with the output content on different lines.
- Println does not require a formatted string or placeholders.
Example:
package main
import "fmt"
func main() {
name := "Alice"
age := 30
// Use Printf for formatted output
fmt.Printf("Name: %s Age: %d\n", name, age)
// Use Println for output
fmt.Println("Name:", name, "Age:", age)
}
// Output
// Name: Alice Age: 30
// Name: Alice Age: 30
Note#
In exported names, the first letter needs to be capitalized. In other words, if a name starts with a capital letter, it is exported.
For example,
fmt.Printf is allowed
fmt.printf is not allowed (Printf needs to be capitalized)
Example:
import (
"fmt"
"math"
)
func main() {
fmt.Println(math.Pi) // Both math.Pi and fmt.Println need to be capitalized
}
Example of using a function:
package main
import "fmt"
func main() {
a := 3
b := 5
// Use Println to output data
fmt.Println("a is", a, "sum is", sum(a, b))
// Use Printf to output data
fmt.Printf("a is %d , sum is %d", a, sum(a, b))
}
// Return a value (sum) by specifying a single return parameter type
// func function_name(input_parameter, input_parameter variable_type) (return_type return_type) {
// Function body
//}
func sum(x, y int) int {
return x + y
}
Variable Declaration#
Use a := "azusa" to quickly declare a variable a with a value of type string. You do not need to manually set the variable type (note that string types need quotation marks). := structure cannot be used outside of a function.
a := "azusa"
b := 123
is equivalent to
var a string = "azusa"
var b int = 123
More examples:
var i, j int = 1, 2
var c, p, j = true, false, "no!"
// c and p are of type bool, j is of type string
var will also automatically determine the variable type.
Variable declarations without an explicit initial value are assigned their zero value.#
The zero values are:
numeric types are 0,
boolean types are false,
strings are "" (empty string).
...