Deleting a key from dictionary keys view

Question

This probably a very basic question but having difficulty search for the correct answer. I have a Python dictionary named raw_data and am extracting the keys separately as follows:

features = raw_data.keys()

A few specific elements of the keys need to be deleted.

del features[137]
del features[160]
del features[181]

The above code however throws an error:

'dict_keys' object doesn't support item deletion

What is the correct way to delete a key form dictionary keys object?

`features = list(raw_data.keys()); del ...`. If you want to delete keys from dict itself `del raw_data[key]` — Sayandip Dutta, Aug 02 '20 at 14:25
Is there any issue with converting to a `list` and then deleting? — Tom, Aug 02 '20 at 14:25
@Ravi: If this is code that was written for Python 2 (where `.keys()` returned a `list`), just wrap the original use of `.keys()` in the `list` constructor. — ShadowRanger, Aug 02 '20 at 14:31
Also: [Delete an element from a dictionary](https://stackoverflow.com/q/5844672/7851470) — Georgy, Aug 02 '20 at 14:42
Do you really want to delete from the dict_view objects and not from the dictionary itself? If yes, what is the reason behind this? — tomanizer, Aug 02 '20 at 14:55
@ShadowRanger You were right. This was an issue with the code being in Python 2. Runs perfectly fine in Python 2 environment. — Ravi, Aug 02 '20 at 16:59

score 2 · Answer 1 · answered Aug 02 '20 at 15:04

'dict_keys' is a view-object.

It provides dynamic view on the dictionary’s entries, which means that when the dictionary changes, the view reflects these changes. https://docs.python.org/3/library/stdtypes.html#dictionary-view-objects

Hence it does not make sense to delete keys in the view without changing the dictionary itself. To delete the keys in the dictionary itself, see @ailin's answer. Following the deletion of keys in the dictionary, the keys will also be deleted in your dict_keys-view object.

If, however, you simply want a list with relevant keys, you can either convert the dict_keys object to a list and filter, or iterate over your dict_keys-object directly and filter the ones you do not need.

relevant_keys = [x for x in features if x not in [137, 160, 181]]

Deleting a key from dictionary keys view

1 Answers1