For loop basics in Go - Mini Project: Build & Apply

For loop basics

📖 Scenario: You work in a small grocery store. You have a list of fruit names that you want to check one by one.

🎯 Goal: You will write a Go program that uses a for loop to go through a list of fruits and print each fruit's name.

📋 What You'll Learn

Create a slice of strings with exact fruit names

Create a variable to count fruits

Use a for loop with index and value to iterate over the slice

Print each fruit name inside the loop

Print the total number of fruits after the loop

💡 Why This Matters

🌍 Real World

Loops are used to process lists of items like products, names, or data entries one by one.

💼 Career

Understanding loops is essential for any programming job because they help automate repetitive tasks efficiently.

1

Create a slice of fruits

Create a slice of strings called fruits with these exact values: "apple", "banana", "cherry", "date", "elderberry".

Go

package main

func main() {
    // Create the slice fruits here
    // Your code here
}

Hint

Use fruits := []string{...} to create the slice with the exact fruit names.

2

Create a counter variable

Create an integer variable called count and set it to 0 to count the fruits.

Go

package main

func main() {
    fruits := []string{"apple", "banana", "cherry", "date", "elderberry"}
    // Create count variable here
    // Your code here
}

Hint

Use count := 0 to create the counter variable.

3

Use a for loop to print fruits

Use a for loop with variables index and fruit to iterate over fruits. Inside the loop, print the fruit name using fmt.Println(fruit) and increase count by 1.

Go

package main

import "fmt"

func main() {
    fruits := []string{"apple", "banana", "cherry", "date", "elderberry"}
    count := 0
    // Write for loop here
    // Your code here
}

Hint

Use for index, fruit := range fruits to loop. Use fmt.Println(fruit) to print each fruit. Increase count by 1 inside the loop.

4

Print the total count

After the loop, print the total number of fruits using fmt.Println("Total fruits:", count).

Go

package main

import "fmt"

func main() {
    fruits := []string{"apple", "banana", "cherry", "date", "elderberry"}
    count := 0
    for index, fruit := range fruits {
        fmt.Println(fruit)
        count++
    }
    // Print total count here
    // Your code here
}

Hint

Use fmt.Println("Total fruits:", count) to show the total number of fruits after the loop.

Practice

1. What does a for loop do in Go programming?

easy

A. Stops the program immediately

B. Imports a package

C. Defines a new variable

D. Repeats a block of code while a condition is true

Solution

1. Step 1: Understand the purpose of a for loop

   A for loop is used to repeat code multiple times based on a condition.

2. Step 2: Identify the correct description

   Only Repeats a block of code while a condition is true correctly describes repeating code while a condition is true.

3. Final Answer:

   Repeats a block of code while a condition is true -> Option D

4. Quick Check:

   For loop = Repeat code [OK]

Hint: For loops repeat code while condition is true [OK]

Common Mistakes:

• Thinking for loop stops program
• Confusing for loop with variable declaration
• Mixing for loop with import statements

2. Which of the following is the correct syntax for a basic for loop in Go?

easy

A. for i := 0; i < 5; i++ { }

B. for (i = 0; i < 5; i++) { }

C. for i in range(5) { }

D. loop i from 0 to 5 { }

Solution

1. Step 1: Recall Go for loop syntax

   Go uses for init; condition; post { } syntax without parentheses.

2. Step 2: Compare options

   for i := 0; i < 5; i++ { } matches Go syntax exactly. Options B, C, and D use other languages or invalid syntax.

3. Final Answer:

   for i := 0; i < 5; i++ { } -> Option A

4. Quick Check:

   Go for loop = for init; condition; post [OK]

Hint: Go for loops use semicolons, no parentheses [OK]

Common Mistakes:

• Using parentheses like in C or Java
• Using Python-style for-in loops
• Writing 'loop' instead of 'for'

3. What is the output of this Go code?

for i := 1; i <= 3; i++ {
    fmt.Print(i, " ")
}

medium

A. 1 2 3

B. 0 1 2 3

C. 1 2 3 4

D. Syntax error

Solution

1. Step 1: Analyze loop range and output

   The loop starts at i=1 and runs while i <= 3, so i takes values 1, 2, 3.

2. Step 2: Understand print output

   Each iteration prints i followed by a space, so output is "1 2 3 "

3. Final Answer:

   1 2 3 -> Option A

4. Quick Check:

   Loop prints 1 to 3 with spaces [OK]

Hint: Check loop start, end, and print inside loop [OK]

Common Mistakes:

• Starting loop at 0 instead of 1
• Including extra number beyond 3
• Confusing print with println

4. Identify the error in this Go for loop:

for i := 0; i < 5 i++ {
    fmt.Println(i)
}

medium

A. Using := instead of = for i

B. Missing semicolon between condition and post statement

C. Using parentheses around for loop

D. Missing curly braces

Solution

1. Step 1: Check for loop syntax parts

   Go requires semicolons between init, condition, and post parts in for loops.

2. Step 2: Locate missing semicolon

   The code misses a semicolon between i < 5 and i++.

3. Final Answer:

   Missing semicolon between condition and post statement -> Option B

4. Quick Check:

   For loop parts separated by semicolons [OK]

Hint: Check semicolons between for loop parts [OK]

Common Mistakes:

• Omitting semicolons in for loop header
• Confusing := with = in loop variable
• Forgetting curly braces

5. How can you use a for loop in Go to sum all even numbers from 2 to 10 inclusive?

hard

A. for i := 2; i < 10; i += 2 { sum += i }

B. for i := 0; i <= 10; i += 2 { sum += i }

C. for i := 1; i <= 10; i++ { if i%2 == 0 { sum += i } }

D. for i := 2; i < 10; i++ { sum += i*2 }

Solution

1. Step 1: Understand the goal

   We want to add even numbers from 2 to 10 inclusive.

2. Step 2: Analyze each option

   for i := 2; i < 10; i += 2 { sum += i } increments by 2 starting at 2, but i < 10 so sums only 2+4+6+8 (misses 10).
   for i := 1; i <= 10; i++ { if i%2 == 0 { sum += i } } loops from 1 to 10, checks if number is even, then adds it. This is correct and clear.
   for i := 2; i < 10; i++ { sum += i*2 } incorrectly multiplies i by 2 and sums, which is wrong.
   for i := 0; i <= 10; i += 2 { sum += i } starts at 0, which includes 0 in sum, not desired.

3. Final Answer:

   for i := 1; i <= 10; i++ { if i%2 == 0 { sum += i } } -> Option C

4. Quick Check:

   Check even with modulo inside loop [OK]

Hint: Use modulo to check even numbers inside loop [OK]

Common Mistakes:

• Starting loop at 0 including unwanted numbers
• Multiplying instead of checking evenness
• Forgetting to check condition inside loop