Going Through Every Key and Value

The problem...

You have a dict with ten entries. Twenty. A hundred.

You need to do something with every key, every value, or every pair.

Writing it out manually isn't an option.

The idea!

You can loop over a dict just like you loop over a list.

The difference: a dict has keys and values. You choose what you loop over.

Looping over keys — default behavior

A for loop on a dict gives you the keys by default:

scores = {"Raven": 85, "Wolf": 74, "Ghost": 91}

for key in scores:
    print(key)

Output:

Raven
Wolf
Ghost

Same as looping over scores.keys() — explicit version:

for key in scores.keys():
    print(key)

Looping over values

scores = {"Raven": 85, "Wolf": 74, "Ghost": 91}

for value in scores.values():
    print(value)

Output:

85
74
91

Looping over key-value pairs

items() gives you both at once — this is what you'll use most:

scores = {"Raven": 85, "Wolf": 74, "Ghost": 91}

for name, score in scores.items():
    print(f"{name}: {score}")

Output:

Raven: 85
Wolf: 74
Ghost: 91

Python unpacks each pair into two variables — the key goes to the first, the value to the second.

Doing something with each pair

scores = {"Raven": 85, "Wolf": 74, "Ghost": 91}

for name, score in scores.items():
    if score >= 80:
        print(f"{name} — passed")

Output:

Raven — passed
Ghost — passed

Building a new dict from a loop

Start with an empty dict and populate it as you go:

scores = {"Raven": 85, "Wolf": 74, "Ghost": 91}
passing = {}

for name, score in scores.items():
    if score >= 80:
        passing[name] = score

print(passing)

Output → {'Raven': 85, 'Ghost': 91}

What's really happening

A for loop on a dict moves through its keys in insertion order.

.values() and .items() give you different slices of the same data.

The dict is never modified by the loop itself.

Heads up!

• Looping directly over a dict gives you keys — not values, not pairs
• Use .items() when you need both key and value — it's the most common pattern
• Don't modify a dict while looping over it — results are unpredictable
• Variable names in for key, value in d.items() are yours — pick readable ones

The mindset shift

Stop thinking: "I need to look up each key manually."

Start thinking: "I loop over the dict and Python hands me each pair directly."

What you should understand now

• Looping over a dict directly gives you keys
• Use .values() to loop over values only
• Use .items() to loop over key-value pairs — the most useful pattern
• Python unpacks each pair into two variables automatically
• Don't modify a dict while looping over it