nestedutils

Nested Utils

The lightweight Python library for safe, simple, dot-notation access to nested dicts and lists. Effortlessly get, set, and delete values deep in your complex JSON, API responses, and config files without verbose error-checking or handling KeyError exceptions.

Why nestedutils?

Working with deeply nested data (like JSON API responses) often leads to verbose, error-prone boilerplate:

# The Standard Way: Verbose and hard to read
user_name = None
if data and "users" in data and len(data["users"]) > 0:
    user = data["users"][0]
    if "profile" in user:
        user_name = user["profile"].get("name")

# With nestedutils: Clean, safe, and readable
from nestedutils import get_path

user_name = get_path(data, "users.0.profile.name")

Features

• Simple Path Syntax: Use dot-notation strings ("a.b.c") or lists (["a", "b", "c"]) to navigate nested structures
• Mixed Data Types: Seamlessly work with dictionaries, lists
• List Index Support: Access list elements using numeric indices, including negative indices
• Auto-creation: Automatically create missing intermediate containers when setting values
• Flexible Fill Strategies: Control how missing containers are created with different fill strategies
• Type Safety: Comprehensive error handling with descriptive error messages and error codes
• Zero Dependencies: Pure Python implementation with no external dependencies

Use Cases

• JSON API Responses: Safely extract values from complex, unpredictable JSON responses without dozens of checks.
• Configuration Management: easily read and modify deeply nested settings in configuration dictionaries.
• Data Transformation: Rapidly remap data from one complex structure to another using get_path and set_path.

Installation

pip install nestedutils

Quick Start

from nestedutils import get_path, set_path, del_path

# Create a nested structure
data = {}

# Set values using dot-notation
set_path(data, "user.name", "John")
set_path(data, "user.age", 30)
set_path(data, "user.hobbies.0", "reading")
set_path(data, "user.hobbies.1", "coding")

# Access values
name = get_path(data, "user.name")  # "John"
age = get_path(data, "user.age")    # 30
first_hobby = get_path(data, "user.hobbies.0")  # "reading"

# Delete values
del_path(data, "user.age")

API Reference

get_path(data, path, default=None)

Retrieve a value from a nested data structure.

Parameters:

• data: The data structure to navigate (dict, list, tuple, or nested combinations)
• path: Path to the value (string with dot notation or list of keys/indices)
• default: Value to return if path doesn't exist (default: None)

Returns: The value at the path, or default if not found

Examples:

data = {"a": {"b": {"c": 5}}}
get_path(data, "a.b.c")  # 5
get_path(data, "a.b.d", default=99)  # 99

data = {"items": [{"name": "apple"}, {"name": "banana"}]}
get_path(data, "items.1.name")  # "banana"
get_path(data, "items.-1.name")  # "banana" (negative index)

set_path(data, path, value, fill_strategy="auto")

Set a value in a nested data structure, creating intermediate containers as needed.

Parameters:

• data: The data structure to modify (must be mutable: dict or list)
• path: Path where to set the value (string with dot notation or list of keys/indices)
• value: The value to set
• fill_strategy: How to fill missing containers (default: "auto")
  • "auto": Intelligently creates {} for dicts, [] for lists
  • "none": Fills missing list items with None
  • "dict": Always creates dictionaries
  • "list": Always creates lists

Examples:

data = {}
set_path(data, "user.profile.name", "Alice")
# Creates: {"user": {"profile": {"name": "Alice"}}}

data = {}
set_path(data, "items.0.name", "Item 1")
# Creates: {"items": [{"name": "Item 1"}]}

data = {}
set_path(data, "items.5", "Item 6", fill_strategy="none")
# Creates: {"items": [None, None, None, None, None, "Item 6"]}

del_path(data, path, allow_list_mutation=False)

Delete a value from a nested data structure.

Parameters:

• data: The data structure to modify
• path: Path to the value to delete
• allow_list_mutation: If True, allows deletion from lists (default: False)

Returns: The deleted value

Raises: PathError if the path doesn't exist or deletion is not allowed

Examples:

data = {"a": {"b": 1, "c": 2}}
del_path(data, "a.b")  # Returns 1, data becomes {"a": {"c": 2}}

data = {"items": [1, 2, 3]}
del_path(data, "items.1", allow_list_mutation=True)  # Returns 2
# data becomes {"items": [1, 3]}

Error Handling

The library uses PathError exceptions with error codes for different failure scenarios:

from nestedutils import PathError, PathErrorCode

try:
    set_path(data, "invalid.path", 1)
except PathError as e:
    print(e.message)  # Error message
    print(e.code)     # Error code (PathErrorCode enum)

Error Codes:

• INVALID_PATH: Invalid path format or type
• INVALID_INDEX: Invalid list index
• MISSING_KEY: Key doesn't exist in dictionary
• EMPTY_PATH: Path is empty
• IMMUTABLE_CONTAINER: Attempted to modify a tuple
• INVALID_FILL_STRATEGY: Invalid fill strategy value

Advanced Usage

Using List Paths

List paths are useful when keys contain dots:

data = {}
set_path(data, ["user.name", "first"], "John")
set_path(data, ["user.name", "last"], "Doe")
# Creates: {"user.name": {"first": "John", "last": "Doe"}}

Negative List Indices

Negative indices work like Python list indexing:

data = {"items": [10, 20, 30]}
get_path(data, "items.-1")  # 30 (last item)
set_path(data, "items.-1", 999)  # Updates last item

Working with Tuples

Tuples are read-only. You can read from them but cannot modify:

data = {"items": (1, 2, 3)}
get_path(data, "items.0")  # 1 (works)
set_path(data, "items.0", 9)  # Raises PathError (tuples are immutable)

Handling None Values

The library can navigate through None values when setting:

data = {"a": None}
set_path(data, "a.b.c", 10)
# Replaces None with container: {"a": {"b": {"c": 10}}}

Requirements

• Python 3.8+

Development

For development setup, building, and contributing, see DEVELOPMENT.md.

Changelog

See CHANGELOG.md for a detailed list of changes and version history.

License

MIT License - see LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Support

If you find this library useful, please consider:

• ⭐ Starring the repository on GitHub to help others discover it.
• 💖 Sponsoring to support ongoing maintenance and development.

Become a Sponsor on GitHub | Support on Patreon

Links

• PyPI: https://pypi.org/project/nestedutils/
• Homepage: https://github.com/ysskrishna/nestedutils
• Repository: https://github.com/ysskrishna/nestedutils.git
• Issues: https://github.com/ysskrishna/nestedutils/issues

Author

Y. Siva Sai Krishna

• GitHub: @ysskrishna
• LinkedIn: ysskrishna