nesteddictionary

Nested Dictionary

Version: 1.2.2

A wrapper for python dicts that allows you to search and navigate through nested dicts using key paths. Also works with mixed dictionaries (mixuture of nested lists and dicts). Derived from a need to search for keys in a nested dictionary; too much time was spent on building yet another full class for nested dictionaries, but it suited our needs.

Quick Start Example:

>>> from nesteddictionary import NestedDict     #import the NestedDict class
>>> d = {'path':{'to':{'key':'val'}}}           #normal way of doing nested dictionary
>>> nested_dict = NestedDict( d )               #created a nested dictionary from a normal dictionary

Features:

• Uses keypaths in subscripting to navigate nested dictionaries ( ex: nested_dict[ ['path','to','key'] ] which is the same as nested_dict['path']['to']['key'] )
• Adds functionality without violating any existing dict operations (that I know of); keypaths are in the form of a list which cannot be used as a key for a normal dict anyway. All other dict rules still apply.
• findall method: Finds all nested keys within a nested dictionary.
• get and set methods: Navigate using a keypath string with seperator ( ex: nested_dict.get('path.to.key') )
• insert method: create a full path to a nested key and set a value, even if the parent keys leading to the destination key don't already exist ( i.e., nested_dict.insert( ['newpath','to','key'], 'newval' ) will add to the existing dictionay, resulting in: NestedDict({ 'path':{'to':{'key':'val'}}, 'newpath':{'to':{'key':'newval'}} }) ).

Limitations:

• While fast, it adds some overhead and therefore cannot ever be as fast as accessing dicts the regular way.

Changes (PEP 440: major.minor.patch):

• v0.1.0: Developed methods for searching keys in nested dictionaries.
• v1.0.1: Initial working version of the nesteddictionary class.
• v1.2.0: Changed dictionary traversing from recursive to functools.reduce; This is less pythonic yet faster (however, still not nearly as fast as directly accessing dicts and list).
• v1.2.2: Minor patch - removes a debugging print statement in the get method.

For comparison, when doing (these are not included in tests, but are easy enough to write and test on your own):

>>> d = [{1:{2:'value'}}]   
>>> %timeit using_reduce(d,[0,1,2])     #reduce from functools
>>> %timeit using_recursion(d,[0,1,2])  #what was used in v1, more pythonic
>>> %timeit d[0][1][2]                  #direct access; fastest

Yields:

>>> 648 ns ± 3.17 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)    #reduce
>>> 1.77 µs ± 4.05 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)   #recursion
>>> 89.3 ns ± 0.448 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each) #direct

References:

• Scalpl: A similar implementation to nested dictionaries. Some good methodology here.
• Functools Reduce for dicts: Speed up dictionary acces, but non-pythonic.
• Others I'm sure I forgot to mention. Thank you.