How to Iterate Through a Dictionary in Python

What you’ll build or solve

You’ll iterate through a Python dictionary to read keys, values, or both at the same time.

When this approach works best

This approach works best when you:

• Need to process key-value data like settings, counters, or user profiles.
• Want to transform a dictionary into a new structure, like a filtered dictionary or a list of results.
• Need to print, validate, or export dictionary contents in a consistent way.

Avoid this approach when:

• You need items ranked or sorted by value. Sort first, then iterate.

Prerequisites

• Python installed
• You know what a dictionary is

Step-by-step instructions

1) Loop over keys (default behavior)

When you iterate over a dictionary directly, you get keys.

scores = {"Mina": 90, "Sam": 82, "Ada": 95}

for name in scores:
    print(name)

This is the same as:

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

2) Use the key to read the value

If you have the key, you can access the value with bracket lookup.

scores = {"Mina": 90, "Sam": 82, "Ada": 95}

for name in scores:
    score = scores[name]
    print(name, score)

3) Loop over values with .values()

Use .values() when you only care about the values.

scores = {"Mina": 90, "Sam": 82, "Ada": 95}

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

This is common for totals and averages:

scores = {"Mina": 90, "Sam": 82, "Ada": 95}
total = 0

for score in scores.values():
    total += score

print(total)

4) Loop over key-value pairs with .items()

Use .items() when you need both key and value.

scores = {"Mina": 90, "Sam": 82, "Ada": 95}

for name, score in scores.items():
    print(name, score)

Examples you can copy

Example 1: Print all settings as key=value

settings = {"theme": "dark", "language": "en", "notifications": True}

for key, value in settings.items():
    print(f"{key}={value}")

Example 2: Filter a dictionary while iterating

prices = {"pen": 1.2, "notebook": 4.5, "backpack": 29.0, "eraser": 0.8}
expensive = {}

for item, price in prices.items():
    if price >= 5:
        expensive[item] = price

print(expensive)

Example 3: Build a list from dictionary data

users = {"Naomi": "Boston", "Sam": "New York", "Ada": "Los Angeles"}
new_york_users = []

for name, city in users.items():
    if city == "New York":
        new_york_users.append(name)

print(new_york_users)

Example 4: Iterate in sorted order

By keys (alphabetical):

scores = {"Mina": 90, "Sam": 82, "Ada": 95}

for name in sorted(scores):
    print(name, scores[name])

By values (highest first):

for name, score in sorted(scores.items(), key=lambda p: p[1], reverse=True):
    print(name, score)

Common mistakes and how to fix them

Mistake 1: Unpacking the wrong thing

What you might do:

scores = {"Mina": 90, "Sam": 82}

for name, score in scores:
    print(name, score)

Why it breaks: Iterating over a dictionary yields keys, not (key, value) pairs, so Python cannot unpack the key into two variables.

Correct approach: Use .items().

scores = {"Mina": 90, "Sam": 82}

for name, score in scores.items():
    print(name, score)

Mistake 2: Changing the dictionary while iterating over it

What you might do:

scores = {"Mina": 90, "Sam": 82, "Ada": 95}

for name in scores:
    if scores[name] < 90:
        del scores[name]

Why it breaks: Modifying a dictionary during iteration can raise RuntimeError and can skip items.

Correct approach: Iterate over a copy of keys.

scores = {"Mina": 90, "Sam": 82, "Ada": 95}

for name in list(scores.keys()):
    if scores[name] < 90:
        del scores[name]

print(scores)

Troubleshooting

If you see ValueError: not enough values to unpack, do this: make sure you’re using .items() when you write for key, value in ....

If you see RuntimeError: dictionary changed size during iteration, do this: iterate over list(d) or list(d.keys()) before deleting or adding keys.

If you see KeyError inside the loop, do this: check that the key exists, or use d.get(key) when keys come from external data.

If you only need values, do this: use .values() to avoid extra lookups.

If you only need keys, do this: loop over the dictionary directly.

Quick recap

• Loop over keys with for key in d (or d.keys()).
• Use the key to access values with d[key].
• Loop over values with for value in d.values().
• Loop over key-value pairs with for key, value in d.items().
• Don’t add or delete keys while iterating. Iterate over a copy of keys if you need to modify the dictionary.