How to create a nested dictionary in Python? Creating a nested dictionary in Python involves defining a dictionary where the values are themselves dictionaries. In this article, I will go over the steps on how to create a nested dictionary in Python. A nested dictionary is a dictionary that contains other dictionaries as its values. This allows you to store data in a hierarchical structure, similar to how you would use nested lists or nested objects in other programming languages.
1. Quick Examples of Creating Nested Dictionary
Below are some quick examples of how to create a nested dictionary. These should give you an idea of how to create a nested dictionary and the below sections explain in detail.
# Quick examples of creating nested dictionary
# Method 1: Create nested dictionary using curly braces {}
nested_dict1 = {
"Python": {
"use": "general-purpose"
},
"C++": {
"use": "systems programming"
}
}
# Method 2: Creating a nested dictionary using the dict()
nested_dict2 = dict(Python=dict(use="general-purpose"),
C=dict(use="systems programming"))
# Method 3: Creating using a dictionary comprehension
nested_dict3 = {language: { "use": use} for language,
use in [("Python", "general-purpose"),
("C++", "systems programming")]
}
# Method 4: Creating using the update() method
nested_dict4 = {}
nested_dict4.update(Python=dict(use="general-purpose"),
C=dict(use="systems programming"))
# Method 5: Nested dictionary from a JSON object
import json
json_str = '''{"Python": {"use": "general-purpose"},
"C++": {"use": "systems programming"}}'''
nested_dict5 = json.loads(json_str)
2. Create Nested Dictionary using {} Notation
One of the most straightforward methods for creating a nested dictionary in Python is using the curly braces {} notation. It allows you to specify the keys and values of the dictionary using a simple syntax. In the case of a nested dictionary, you can create a dictionary with keys that point to dictionaries as values.
2.1 Syntax of Curly Braces {}
To create a dictionary using the curly braces {} notation, you can use the following syntax:
# Syntax using curly {}
nested_dict = {
key1: {
inner_key1: inner_value1,
inner_key2: inner_value2,
...
},
key2: {
inner_key1: inner_value1,
inner_key2: inner_value2,
...
},
...
}
2.2 Create Nested Dictionary Example
The example creates a nested dictionary called languages with three keys: “Py”, “Java”, and “C#”. Each of these keys points to another dictionary as its value. The nested dictionary can be accessed and modified using the keys and the dot notation.
# Create nested dictionary
languages = {
"Py": {
"year": 1991,
"creator": "G. van Rossum",
},
"Java": {
"year": 1995,
"creator": "J. Gosling",
},
"C#": {
"year": 2000,
"creator": "Microsoft",
}
}
print(languages )
3. Creating Nested Dictionary Using dict() Constructor
The dict() constructor is a built-in function in Python that allows you to create a dictionary. It can be used to create a nested dictionary by providing it with key-value pairs where the values are dictionaries themselves.
Check an example of creating a nested dictionary that stores information about different programming languages using the dict() constructor.
# Create using dict()
languages = dict(
Py=dict(year=1991, creator="G. van Rossum"),
Java=dict(year=1995, creator="J. Gosling"),
C_Sharp=dict(year=2000, creator="Microsoft")
)
print(languages)
4. Creating Nested Dictionary Using Comprehension
A dictionary comprehension allows you to create a dictionary by specifying the keys and values using a single line of code. You can also use dictionary comprehension to create a nested dictionary, which is a dictionary that has keys that point to dictionaries as values.
# Create using Dictionary Comprehension
languages = {
language: { "year": year, "creator": creator}
for language, year, creator in [
("Py", 1991, "G. van Rossum"),
("Java", 1995, "J. Gosling"),
("C#", 2000, "Microsoft")
]
}
print(languages)
5. Using update() Method
The update() method is a built-in method in Python that allows you to update the keys and values of a dictionary that can also be used to create a nested dictionary. It takes a dictionary as an argument and adds the key-value pairs of that dictionary to the original dictionary.
# Update update() Method
languages = {}
languages.update({"Py": {"year": 1991, "creator": "G. van Rossum"}})
languages.update({"Java": {"year": 1995, "creator": "J. Gosling"}})
languages.update({"C#": {"year": 2000, "creator": "Microsoft"}})
print(languages)
6. Creating from a JSON Object
If you are creating a nested dictionary from JSON, you can use the json.loads() method to create a nested dictionary from a JSON object that has nested keys and values. The json.loads() method is a built-in method in Python that allows you to parse a JSON string and create a dictionary from it.
# From json file
import json
json_string = '''{
"Python": {"year": 1991, "creator": "G. van Rossum"},
"Java": {"year": 1995, "creator": "J. Gosling"},
"C#": {"year": 2000, "creator": "Microsoft"}
}'''
languages = json.loads(json_string)
print(languages)
7. Common Operations on Nested Dictionary in Python
A nested dictionary is a dictionary that has keys that point to dictionaries as values. Once you have created a nested dictionary, you may want to perform various operations on it, such as accessing, modifying, adding, and deleting elements.
These are some of the examples of operations that are most common.
# Accessing elements of a nested dictionary
print(languages["Py"]["year"])
# Output:
# 1991
# Modifying elements in a nested dictionary
languages["Py"]["year"] = 1992
# Adding new elements to a nested dictionary
languages["Py"]["use"] = "web development"
# Deleting elements from a nested dictionary
del languages["Py"]["use"]
# Looping through a nested dictionary
for outer_key, inner_dict in languages.items():
for inner_key, value in inner_dict.items():
print(f"{outer_key}.{inner_key}: {value}")
Besides these there are several Python Dictionary Methods that are used to perform operations on nested dictionaries.
Frequently Asked Questions on Create Nested Dictionary in Python
Nested dictionary in Python is a dictionary within another dictionary. This means that the values of the outer dictionary are themselves dictionaries. This allows you to create a hierarchical structure, providing a way to organize and manage data more efficiently.
You can create an empty nested dictionary by initializing an empty dictionary as the value for a key in another dictionary. This creates a dictionary with an outer key 'outer_key' whose value is an empty dictionary {}.
You can convert a nested dictionary to a JSON string in Python using the json module. The json.dumps() function is used to serialize a Python object (in this case, a dictionary) to a JSON-formatted string.
To add values to a nested dictionary, you can reference the keys of the outer and inner dictionaries and assign values
You can create a nested dictionary with multiple levels by adding more layers of dictionaries. Each additional layer represents a deeper level of nesting.
To access values in a nested dictionary in Python, you need to use the keys of each level to navigate through the hierarchy. You can do this by chaining square brackets for each level.
Summary and Conclusion
In this article, you have learned about how to create a nested dictionary in Python using various methods. If you have any questions about creating or working with nested dictionaries in Python, feel free to ask! I will do my best to help.
Happy Learning!!
Related Articles
- Python Max Value in Dictionary
- Convert String to Dictionary Python
- Convert List into Dictionary in Python
- How to Convert Dictionary to String Python?
- Get the Index of Key in Python Dictionary
- How to Create Python Empty Dictionary?
- How to Zip Dictionary in Python
- Python Dictionary Comprehension
- Python Dictionary keys() Method Usage
- Iterate Python Dictionary using enumerate() Function
- Copy the Dictionary and edit it in Python
- Convert Two Lists into Dictionary in Python
