Python Dictionary Methods

Table of Contents

In the last lesson, we learned about Python Dictionary Operations. Now let’s use dictionary methods to access, update, and remove data safely.

🧩 Let’s Talk About Tools for Dictionaries

We have a dictionary. We know how to access values. We know how to add and remove items.

But there are many built-in methods that make working with dictionaries easier. These are functions that belong to dictionary objects. They let us do things like get values safely, update multiple items, remove items, copy the dictionary, and more.

Let’s go through the most common dictionary methods.

⚙️ Getting Values Safely — get() in Python

The get() method returns the value for a key. If the key does not exist, it returns None instead of raising an error. We can also provide a default value.

person = {"name": "Alex", "age": 25}
print(person.get("name"))
print(person.get("city"))
print(person.get("city", "Unknown"))

Output

Alex
None
Unknown

This is safer than using square brackets. Let’s use it when we are not sure if the key exists.

💡 Setting a Default — setdefault() in Python

setdefault() returns the value for a key. If the key does not exist, it inserts the key with a default value and returns that default.

person = {"name": "Alex", "age": 25}
person.setdefault("city", "London")
print(person)

Output

{'name': 'Alex', 'age': 25, 'city': 'London'}

If the key already exists, setdefault() does nothing and returns the existing value.

person.setdefault("name", "Sam")
print(person["name"])

Output

Alex

The name is still “Alex”. Because it already existed.

🧪 Getting All Keys, Values, and Items in Python

Dictionaries have three view methods.

keys() returns a view of all keys.
values() returns a view of all values.
items() returns a view of all key-value pairs as tuples.

person = {"name": "Alex", "age": 25, "city": "London"}
print(person.keys())
print(person.values())
print(person.items())

Output

dict_keys(['name', 'age', 'city'])
dict_values(['Alex', 25, 'London'])
dict_items([('name', 'Alex'), ('age', 25), ('city', 'London')])

These are not lists. They are view objects. But we can loop over them, or convert them to lists if needed.

print(list(person.keys()))

Output

['name', 'age', 'city']

They are dynamic. If we change the dictionary, the view updates.

📌 Updating a Dictionary — update() in Python

The update() method adds all key-value pairs from another dictionary or iterable of key-value pairs. It modifies the dictionary in place.

dict1 = {"a": 1, "b": 2}
dict2 = {"b": 3, "c": 4}
dict1.update(dict2)
print(dict1)

Output

{'a': 1, 'b': 3, 'c': 4}

We can also update with an iterable of pairs.

dict1.update([("d", 5), ("e", 6)])
print(dict1)

Output

{'a': 1, 'b': 3, 'c': 4, 'd': 5, 'e': 6}

🏗️ Removing Items — pop(), popitem(), clear() in Python

pop(key) removes the key and returns its value. If the key is not found, it raises a KeyError, unless we provide a default.

person = {"name": "Alex", "age": 25, "city": "London"}
age = person.pop("age")
print(age)
print(person)

Output

25
{'name': 'Alex', 'city': 'London'}

person.pop("country", "Not found")

Output

'Not found'

popitem() removes and returns the last inserted key-value pair as a tuple. In Python 3.7+, it removes the last item.

person = {"name": "Alex", "age": 25, "city": "London"}
item = person.popitem()
print(item)
print(person)

Output

('city', 'London')
{'name': 'Alex', 'age': 25}

clear() removes all items.

person.clear()
print(person)

Output

{}

🔍 Copying a Dictionary — copy() in Python

The copy() method returns a shallow copy of the dictionary.

original = {"a": 1, "b": 2}
copied = original.copy()
print(copied)

Output

{'a': 1, 'b': 2}

We can also use dict(original). For deep copies, we use copy.deepcopy() from the copy module.

🧭 Creating a Dictionary from Keys — fromkeys() in Python

fromkeys() is a class method that creates a new dictionary from a sequence of keys, all with the same value.

keys = ["a", "b", "c"]
new_dict = dict.fromkeys(keys)
print(new_dict)

Output

{'a': None, 'b': None, 'c': None}

We can provide a value.

new_dict = dict.fromkeys(keys, 0)
print(new_dict)

Output

{'a': 0, 'b': 0, 'c': 0}

That is useful for initializing a dictionary with default values.