Python Dictionaries Explained Simply (Keys, Values, and Access)

Dictionaries store data as key-value pairs. They are useful when you need to look up values quickly using a unique key instead of an index.

What is a dictionary?

A dictionary is created with curly braces {}. Each item is a pair: a key followed by a colon : and a value. Pairs are separated by commas.

person = {
    "name": "Alex",
    "age": 25,
    "city": "Berlin"
}

settings = {
    "theme": "dark",
    "notifications": True,
    "volume": 75
}

You can also create an empty dictionary:

empty_dict = {}

Keys are usually strings or numbers. Values can be any type.

Accessing values with keys

Use square brackets [] and the key to get a value.

print(person["name"])  # Alex
print(person["age"])   # 25

Modifying and adding items

Dictionaries are mutable. Change a value with its key:

person["age"] = 26
print(person["age"])  # 26

Add a new key-value pair the same way:

person["job"] = "Developer"
print(person["job"])  # Developer

Key differences: list vs dictionary

• A list uses numeric indexes (0, 1, 2...) to access items in order.
• A dictionary uses custom keys (often strings) to access values directly.

Example comparison:

# List: access by position
fruits_list = ["apple", "banana", "cherry"]
print(fruits_list[1])  # banana

# Dictionary: access by key
fruits_dict = {
    "first": "apple",
    "second": "banana",
    "third": "cherry"
}
print(fruits_dict["second"])  # banana

Dictionaries are faster for lookups when keys are meaningful.

Common examples

Simple translation dictionary:

translate = {
    "hello": "hallo",
    "goodbye": "auf Wiedersehen",
    "thanks": "danke"
}

print(translate["hello"])  # hallo
translate["yes"] = "ja"

User information:

user = {
    "username": "alex123",
    "email": "[e-mail]",
    "active": True
}

print(user["email"])  # [e-mail]

Common mistake: KeyError

If you try to access a key that does not exist, Python raises an error.

print(person["phone"])  # KeyError: 'phone'

Check if a key exists first, or use .get() which returns None if missing:

print(person.get("phone"))  # None

Quick summary

• Create dictionaries with curly braces and key-value pairs.
• Access and modify values using keys in square brackets.
• Add new items by assigning to a new key.
• Keys must be unique; use meaningful names.
• Dictionaries are key-based, unlike order-based lists.

Practice building small dictionaries for real data. They are essential for organizing information in Python programs.