Is there any other way to delete an item in a dictionary only if the given key exists, other than:
if key in mydict:
del mydict[key]
The scenario is that I'm given a collection of keys to be removed from a given dictionary, but I am not certain if all of them exist in the dictionary. Just in case I miss a more efficient solution.
This question is related to
python
python-2.7
There is also:
try:
del mydict[key]
except KeyError:
pass
This only does 1 lookup instead of 2. However, except
clauses are expensive, so if you end up hitting the except clause frequently, this will probably be less efficient than what you already have.
Let's call keys
the list/iterator of keys that you are given to remove. I'd do this:
keys_to_remove = set(keys).intersection(set(mydict.keys()))
for key in keys_to_remove:
del mydict[key]
You calculate up front all the affected items and operate on them.
I prefer to create a new dictionary over mutating an existing one, so I would probably also consider this:
keys_to_keep = set(mydict.keys()) - set(keys)
new_dict = {k: v for k, v in mydict.iteritems() if k in keys_to_keep}
or:
keys_to_keep = set(mydict.keys()) - set(keys)
new_dict = {k: mydict[k] for k in keys_to_keep}
Source: Stackoverflow.com