Dictionary iteration in Python - Step-by-Step Execution

Concept Flow - Dictionary iteration

Start with dictionary

↓

Pick one key-value pair

↓

Use key and/or value

↓

More pairs?

Yes→Pick next pair

No↓

End

We start with a dictionary, pick each key-value pair one by one, use them, and repeat until all pairs are processed.

Execution Sample

Python

my_dict = {'a': 1, 'b': 2, 'c': 3}
for key, value in my_dict.items():
    print(key, value)

This code goes through each key and value in the dictionary and prints them.

Execution Table

Step	Current Pair	Key	Value	Action	Output
1	('a', 1)	a	1	Print key and value	a 1
2	('b', 2)	b	2	Print key and value	b 2
3	('c', 3)	c	3	Print key and value	c 3
4	No more pairs	-	-	Loop ends	-

💡 All key-value pairs have been processed, loop ends.

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
key	-	a	b	c	-
value	-	1	2	3	-

Key Moments - 2 Insights

Why do we use .items() to get both key and value?

Using .items() returns pairs of key and value together, so in each loop step we get both. Without .items(), looping over the dictionary gives only keys (see execution_table rows 1-3).

What happens if the dictionary is empty?

The loop body does not run at all because there are no pairs to pick. The loop ends immediately (like step 4 in execution_table).

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'key' at step 2?

A b

B a

C c

D -

💡 Hint

Check the 'key' column in variable_tracker after step 2.

At which step does the loop stop running?

A Step 3

B Step 2

C Step 4

D Step 1

💡 Hint

Look at the exit_note and the last row in execution_table.

If we looped over my_dict without .items(), what would the loop variable hold?

A Values only

B Keys only

C Key-value pairs

D Nothing

💡 Hint

Recall the key_moments explanation about .items() and dictionary iteration.

Concept Snapshot

Dictionary iteration:
Use for key, value in dict.items():
  to get each key and its value.
Without .items(), loop gives keys only.
Loop runs once per key-value pair.
Stops when all pairs are done.

Full Transcript

Dictionary iteration means going through each key and value in a dictionary one by one. We use a for loop with .items() to get both key and value together. In each step, the loop picks one pair, lets us use the key and value, then moves to the next. When no pairs remain, the loop ends. If the dictionary is empty, the loop does not run. Without .items(), looping over a dictionary gives only keys, not values. This is important to remember when you want both parts. The example code prints each key and value. The execution table shows each step clearly, with the current pair, key, value, and output. The variable tracker shows how key and value change each step. This helps beginners see exactly what happens inside the loop.