Output formatting basics in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Go code using fmt.Printf?

Consider the following Go code snippet. What will it print to the console?

Go

package main

import "fmt"

func main() {
    x := 42
    y := 3.14159
    fmt.Printf("x = %d, y = %.2f\n", x, y)
}

A x = 42, y = 3.1416

B x = 42, y = 3.14159

C x = 42, y = 3.14

D x = 42, y = 3.1

💡 Hint

Look at the %.2f format specifier. It controls how many decimal places are shown.

The %.2f format prints the floating-point number rounded to 2 decimal places. So 3.14159 becomes 3.14.

❓ Predict Output

intermediate

What does this Go code print with width formatting?

What is the output of this Go program that uses width specifiers in fmt.Printf?

Go

package main

import "fmt"

func main() {
    name := "Go"
    fmt.Printf("|%10s|%-10s|\n", name, name)
}

A | Go|Go |

B |Go | Go|

C | Go |Go |

D | Go| Go|

💡 Hint

The %10s means right-align in 10 spaces, %-10s means left-align in 10 spaces.

The first %10s prints the string right-aligned in 10 spaces, so spaces come first. The second %-10s prints left-aligned, so spaces come after.

❓ Predict Output

advanced

What is the output of this Go code using fmt.Sprintf with multiple verbs?

What string does this Go code produce?

Go

package main

import "fmt"

func main() {
    s := fmt.Sprintf("%d + %d = %d", 7, 5, 7+5)
    fmt.Println(s)
}

A 7 + 5 = 0

B 7 + 5 = 7+5

C 7 + 5 = 75

D 7 + 5 = 12

💡 Hint

fmt.Sprintf formats the string with the given values replacing %d verbs.

Each %d is replaced by the corresponding integer argument. So 7, 5, and 12 (7+5) are inserted.

❓ Predict Output

advanced

What error does this Go code produce?

What happens when you run this Go code?

Go

package main

import "fmt"

func main() {
    fmt.Printf("%d %s", 10)
}

A 10 %s

B runtime error: missing argument for %s

C 10

D Compilation error: wrong number of arguments

💡 Hint

Check if the number of verbs matches the number of arguments.

The format string expects two arguments (%d and %s), but only one (10) is given. This causes a runtime error.

🧠 Conceptual

expert

How many items are printed by this Go code with fmt.Printf and a slice?

What is the output count of items printed by this Go code snippet?

Go

package main

import "fmt"

func main() {
    nums := []int{1, 2, 3}
    fmt.Printf("%v %v %v %v", nums[0], nums[1], nums[2], nums)
}

A Prints 4 items: 1 2 3 [1 2 3]

B Prints 3 items: 1 2 3

C Prints 1 item: [1 2 3]

D Compilation error: cannot print slice with %v

💡 Hint

Each %v corresponds to one argument. The last argument is the whole slice.

The code prints four items: the three integers and then the slice printed as [1 2 3].