Python Dictionary Examples

Overview

Short, copy-paste examples for the most common dictionary tasks in Python. Run any of them in the online Python compiler.

Examples

Merge two dictionaries

a = {"x": 1}
b = {"y": 2}
print(a | b)   # {'x': 1, 'y': 2}  (Python 3.9+)

Get a value safely with get()

d = {"name": "Ada"}
print(d.get("name"))            # Ada
print(d.get("email", "n/a"))    # n/a  (default, no KeyError)

List the keys

d = {"a": 1, "b": 2, "c": 3}
print(list(d.keys()))   # ['a', 'b', 'c']

List the values

d = {"a": 1, "b": 2, "c": 3}
print(list(d.values()))   # [1, 2, 3]

Loop over items()

prices = {"pen": 3, "book": 12}
for name, cost in prices.items():
    print(name, cost)
# pen 3
# book 12

Iterate keys and values separately

d = {"a": 1, "b": 2}
for k in d:
    print(k, d[k])
# a 1
# b 2

Build a dict with a comprehension

words = ["hi", "hey", "hello"]
print({w: len(w) for w in words})   # {'hi': 2, 'hey': 3, 'hello': 5}

Invert keys and values

d = {"a": 1, "b": 2}
print({v: k for k, v in d.items()})   # {1: 'a', 2: 'b'}

Count occurrences

from collections import Counter
votes = ["a", "b", "a", "c", "a"]
print(dict(Counter(votes)))   # {'a': 3, 'b': 1, 'c': 1}

Frequently asked questions

How do I merge two dictionaries in Python?

On Python 3.9+, use a | b; on older versions use {a, b}. Both return a new dict where later keys win.

How do I read a dictionary value without a KeyError?

Use d.get(key, default) — it returns the default (or None) instead of raising when the key is missing.

How do I invert a dictionary?

Use a comprehension over its items: {v: k for k, v in d.items()}. Values must be unique and hashable.