Deleting map entries in Go - Step-by-Step Execution

Concept Flow - Deleting map entries

Start with map initialized

↓

Check if key exists in map?

No→End: Nothing to delete

Yes↓

Delete key from map

↓

Key removed, map updated

↓

End

The flow starts with a map, checks if a key exists, deletes it if found, and ends with the updated map.

Execution Sample

Go

m := map[string]int{"a":1, "b":2, "c":3}
delete(m, "b")
fmt.Println(m)

This code deletes the key "b" from the map and prints the updated map.

Execution Table

Step	Operation	Map State	Key Checked	Action	Resulting Map
1	Initialize map	{}	N/A	Create map with keys a,b,c	{"a":1, "b":2, "c":3}
2	Check key existence	{"a":1, "b":2, "c":3}	"b"	Key exists	No change
3	Delete key	{"a":1, "b":2, "c":3}	"b"	Delete key "b"	{"a":1, "c":3}
4	Print map	{"a":1, "c":3}	N/A	Output map	{"a":1, "c":3}
5	End	{"a":1, "c":3}	N/A	No more operations	Final map state

💡 Key "b" deleted, map no longer contains "b"

Variable Tracker

Variable	Start	After Step 1	After Step 3	Final
m	nil	{"a":1, "b":2, "c":3}	{"a":1, "c":3}	{"a":1, "c":3}

Key Moments - 2 Insights

Why does the map still exist after deleting a key?

Deleting a key removes only that entry; the map itself remains intact as shown in execution_table step 3 and 4.

What happens if we delete a key that does not exist?

Deleting a non-existent key does nothing and does not cause an error, similar to step 2 where key existence is checked.

Visual Quiz - 3 Questions

Look at the execution table, what is the map state after step 3?

A {"a":1, "b":2, "c":3}

B {"a":1, "c":3}

C {"b":2, "c":3}

D {}

💡 Hint

Check the 'Resulting Map' column at step 3 in the execution_table.

At which step is the key "b" confirmed to exist before deletion?

A Step 3

B Step 1

C Step 2

D Step 4

💡 Hint

Look at the 'Key Checked' and 'Action' columns in the execution_table.

If we tried to delete key "d" which is not in the map, what would happen?

A Map would be unchanged

B Program would crash

C All keys would be deleted

D Key "d" would be added

💡 Hint

Refer to key_moments about deleting non-existent keys and execution_table step 2.

Concept Snapshot

Deleting map entries in Go:
- Use delete(map, key) to remove a key.
- If key exists, it is removed; map stays valid.
- Deleting a non-existent key does nothing.
- Map remains usable after deletion.
- No error occurs when deleting missing keys.

Full Transcript

This visual trace shows how deleting a key from a Go map works. We start with a map containing keys a, b, and c. We check if key b exists, then delete it. After deletion, the map no longer contains b but still has a and c. Printing the map confirms the change. Deleting a key does not remove the map itself. If a key does not exist, deleting it does nothing and causes no error.