Iterating over maps in Go - Step-by-Step Execution

Concept Flow - Iterating over maps

Start

↓

Initialize map

↓

Start loop over map

↓

Get key, value

↓

Process key, value

↓

More items?

Yes→Next item

No↓

End loop

↓

Program ends

This flow shows how Go loops over each key-value pair in a map until all items are processed.

Execution Sample

Go

package main
import "fmt"
func main() {
  m := map[string]int{"a":1, "b":2}
  for k, v := range m {
    fmt.Println(k, v)
  }
}

This code loops over a map and prints each key and its value.

Execution Table

Step	Action	Key	Value	Output
1	Start loop
2	Get first item	a	1	Print: a 1
3	Get second item	b	2	Print: b 2
4	No more items			Loop ends

💡 All map items processed, loop ends

Variable Tracker

Variable	Start	After 1	After 2	Final
k		a	b
v		1	2

Key Moments - 2 Insights

Why does the order of keys printed change each time?

Go maps do not guarantee order when iterating. The execution_table shows keys 'a' then 'b', but this can vary each run.

What happens if the map is empty?

The loop body does not run at all. The execution_table would skip steps 2 and 3 and go directly to step 4.

Visual Quiz - 3 Questions

Look at the execution_table, what is the key and value at step 3?

A Key: a, Value: 1

B Key: b, Value: 2

C Key: c, Value: 3

D No key, no value

💡 Hint

Check row with Step 3 in execution_table for key and value

At which step does the loop end according to the execution_table?

A Step 4

B Step 3

C Step 2

D Step 1

💡 Hint

Look for the step where 'Loop ends' is in the Output column

If the map had 3 items, how many times would the loop run?

A 1 time

B 2 times

C 3 times

D 4 times

💡 Hint

Loop runs once per map item, see variable_tracker for iterations

Concept Snapshot

Go maps store key-value pairs.
Use 'for k, v := range map' to loop over them.
Each loop gets one key and its value.
Order is random, not guaranteed.
Loop ends after all items processed.

Full Transcript

This visual execution shows how Go iterates over maps using a for loop with range. The program initializes a map with two items. Then it starts a loop that runs once for each key-value pair. Each step gets one key and value, then prints them. The order of keys is not fixed and can change each run. The loop ends when all items are processed. Variables k and v change each iteration to hold the current key and value. Beginners often wonder why order changes or what happens if the map is empty. The execution table and variable tracker clarify these points. The quiz tests understanding of keys, loop steps, and iteration count.