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Loops & Iteration

for, while, enumerate, zip, range — and their equivalents.

for ... in

fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)

fruits := []string{"apple", "banana", "cherry"}
for _, fruit := range fruits {
    fmt.Println(fruit)
}

enumerate

fruits = ["apple", "banana", "cherry"]
for i, fruit in enumerate(fruits):
    print(f"{i}: {fruit}")

fruits := []string{"apple", "banana", "cherry"}
for i, fruit := range fruits {
    fmt.Printf("%d: %s\n", i, fruit)
}

dict.items()

scores = {"alice": 90, "bob": 85}
for name, score in scores.items():
    print(f"{name}: {score}")

scores := map[string]int{"alice": 90, "bob": 85}
for name, score := range scores {
    fmt.Printf("%s: %d\n", name, score)
}

while

n = 10
while n > 0:
    n -= 1

// Go has no "while" keyword — use "for" with a condition
n := 10
for n > 0 {
    n--
}

while True

while True:
    line = input()
    if line == "quit":
        break

scanner := bufio.NewScanner(os.Stdin)
for {
    scanner.Scan()
    if scanner.Text() == "quit" {
        break
    }
}

range

for i in range(5):          # 0, 1, 2, 3, 4
    print(i)

for i in range(2, 8, 2):   # 2, 4, 6
    print(i)

for i := range 5 {          // 0, 1, 2, 3, 4 (Go 1.22+)
    fmt.Println(i)
}

for i := 2; i < 8; i += 2 { // 2, 4, 6
    fmt.Println(i)
}

zip

names = ["alice", "bob"]
scores = [90, 85]
for name, score in zip(names, scores):
    print(f"{name}: {score}")

// Go has no built-in zip — use an index loop instead
names := []string{"alice", "bob"}
scores := []int{90, 85}
for i := 0; i < len(names) && i < len(scores); i++ {
    fmt.Printf("%s: %d\n", names[i], scores[i])
}

range copies the value

for _, v := range slice gives you a copy of each element. Modifying v does not affect the original slice. Use the index to modify in place:

for i := range items {
    items[i].Count++  // modifies the original element
}