Python - Flatten and remove keys from Dictionary

Python - Flatten and remove keys from Dictionary

Let's create a tutorial on how to flatten a nested dictionary and simultaneously remove certain keys from it.

Introduction:

Given a nested dictionary, our goal is to flatten it into a single level dictionary and also have the ability to remove certain keys during this process.

For instance: Dictionary:

{ 'a': 1, 'b': {'c': 2, 'd': {'e': 3, 'f': {'g': 4}}}, 'h': 5 }

Flattening this dictionary (while removing keys 'c' and 'f') should result in:

{ 'a': 1, 'b.d.e': 3, 'h': 5 }

Step-by-step Solution:

  1. Recursive Function to Flatten Dictionary: We'll use a recursive function to traverse through the dictionary, building the flattened keys and removing unwanted ones.

    def flatten_dict(d, parent_key='', sep='.', keys_to_remove=None): items = {} keys_to_remove = keys_to_remove or [] for k, v in d.items(): if k in keys_to_remove: continue new_key = f"{parent_key}{sep}{k}" if parent_key else k if isinstance(v, dict): items.update(flatten_dict(v, new_key, sep=sep, keys_to_remove=keys_to_remove)) else: items[new_key] = v return items

  2. Example Usage:

    nested_dict = { 'a': 1, 'b': {'c': 2, 'd': {'e': 3, 'f': {'g': 4}}}, 'h': 5 } unwanted_keys = ['c', 'f'] flattened = flatten_dict(nested_dict, keys_to_remove=unwanted_keys) print(flattened) # This will output {'a': 1, 'b.d.e': 3, 'h': 5}

Tips:

  • The recursion approach is useful when dealing with nested dictionaries of arbitrary depths.

  • Providing keys_to_remove as an optional argument with a default value of None makes our function more flexible, allowing users to decide which keys they want to exclude.

Conclusion:

Flattening a dictionary while also having the option to remove certain keys is a useful operation, especially when working with complex data structures or preparing data for certain applications. With Python's capabilities for handling dictionaries and a recursive approach, we can efficiently transform nested dictionaries into their flattened versions while filtering out unwanted keys. Whether you're cleaning data or restructuring it for storage or presentation, Python provides a powerful and flexible way to achieve your goals.

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