Convert a Nested OrderedDict to Dict - Python

The task of converting a nested OrderedDict to a regular dictionary in Python involves recursively transforming each OrderedDict including nested ones into a standard dictionary. This ensures that all OrderedDict instances are replaced with regular dict objects, while maintaining the original structure and key-value mappings.

For example, we have an OrderedDict like a = OrderedDict([('1', 'one'), ('2', OrderedDict([('-2', '-ive'), ('+2', '+ive')]))]). The task is to convert this nested OrderedDict into a regular dictionary. After conversion, the output will be <class 'dict'> {'1': 'one', '2': {'-2': '-ive', '+2': '+ive'}}.

Using dict()

dict() directly converts the OrderedDict into a regular dictionary and it can handle nested OrderedDict instances recursively. By iterating through the items and using a conditional to check for nested OrderedDict objects, this method ensures that even deeply nested structures are properly converted. It avoids unnecessary serialization or deserialization, making it an optimal choice for most cases.

from collections import OrderedDict

a = OrderedDict([('1', 'one'), ('2', OrderedDict([('-2', '-ive'), ('+2', '+ive')]))])

# Direct conversion
b = dict((k, dict(v) if isinstance(v, OrderedDict) else v) for k, v in a.items())

print(type(b), b)

<class 'dict'> {'1': 'one', '2': {'-2': '-ive', '+2': '+ive'}}

Explanation:

• for k, v in a.items() iterates over key-value pairs in a, where k is the key and v is the value.
• if isinstance(v, OrderedDict) checks if v is an OrderedDict.
• dict(v) converts v to a regular dict if it’s an OrderedDict.
• else v keeps v unchanged if it’s not an OrderedDict.
• Then constructs a new dictionary b from the processed key-value pairs.

Using json.dumps()

This method serializes the OrderedDict into a JSON string and then deserializes it back into a regular dictionary. While this approach is useful when working with data that needs to be serialized for storage or transfer, it is generally slower than the dict() method due to the overhead of serializing and deserializing the data. This method might be more appropriate if we're dealing with data that requires serialization for other purposes.

import json
from collections import OrderedDict

a = OrderedDict([('1', 'one'), ('2', OrderedDict([('-2', '-ive'), ('+2', '+ive')]))])

# Direct conversion
b = json.loads(json.dumps(a))

print(type(b), b)

<class 'dict'> {'1': 'one', '2': {'-2': '-ive', '+2': '+ive'}}

Explanation:

• json.dumps(a) converts the OrderedDict a into a JSON string representation.
• json.loads(...) parses the JSON string back into a regular Python dictionary.

Using recursion

In this method, we recursively iterate over the OrderedDict, copying each key-value pair and checking for nested OrderedDict objects. This is efficient, but since it requires a bit more code and involves the overhead of copying elements, it can be slower than using the dict() ,especially for larger or more deeply nested structures.

from collections import OrderedDict

a = OrderedDict([('1', 'one'), ('2', OrderedDict([('-2', '-ive'), ('+2', '+ive')]))])

 # Recursive function 
def fun(a):
    if isinstance(a, OrderedDict):
        d = {}
        for k, v in a.items():
            d[k] = fun(v) if isinstance(v, OrderedDict) else v
        return d
    return a

b = fun(a) # function calling
print(type(b), b)

<class 'dict'> {'1': 'one', '2': {'-2': '-ive', '+2': '+ive'}}

Explanation:

• fun(a) recursively converts an OrderedDict and any nested OrderedDict objects to regular dict by iterating through each key-value pair.
• If a value is an OrderedDict, it calls fun to convert it, while non-OrderedDict values are left unchanged.