How to Efficiently Filter Dictionary Keys in Python?

Selective Filtering of Dictionary Keys

Working with dictionaries, you may encounter situations where you only need a subset of keys. Instead of manually selecting and copying the desired data, Python offers efficient methods to filter dictionaries.

Constructing a New Dictionary

To create a new dictionary containing only specific keys, you can utilize dictionary comprehension:

new_dict = {key: old_dict[key] for key in desired_keys}

This code reads old_dict, iterates over desired_keys, and creates a new key-value pair for each match in new_dict.

In-Place Modification

If you want to modify the existing dictionary, the following approach removes unwanted keys:

unwanted_keys = set(old_dict.keys()) - set(desired_keys)
for key in unwanted_keys:
    del old_dict[key]

This method calculates a set of keys to remove (unwanted_keys) and then iterates through them, deleting each key from old_dict.

Performance Considerations

When using the in-place modification approach, note that the iteration over unwanted keys is proportional to the size of the original dictionary. This can be inefficient for large dictionaries.

The above is the detailed content of How to Efficiently Filter Dictionary Keys in Python?. For more information, please follow other related articles on the PHP Chinese website!