Python Dictionary – How to Remove a Key from a Python Dictionary

dictionarypythonunset

I want to remove a key from a dictionary if it is present. I currently use this code:

if key in my_dict:
    del my_dict[key]

Without the if statement, the code will raise KeyError if the key is not present. How can I handle this more simply?

_{See Delete an element from a dictionary for more general approaches to the problem of removing a key from a dict (including ones which produce a modified copy).}

Best Answer

To delete a key regardless of whether it is in the dictionary, use the two-argument form of dict.pop():

my_dict.pop('key', None)

This will return my_dict[key] if key exists in the dictionary, and None otherwise. If the second parameter is not specified (i.e. my_dict.pop('key')) and key does not exist, a KeyError is raised.

To delete a key that is guaranteed to exist, you can also use

del my_dict['key']

This will raise a KeyError if the key is not in the dictionary.

Related Solutions

Python – How to Remove Certain Keys from a Dictionary in Python

Iterate over the return value from .keys() instead. Since you get a list of keys back, it won't be affected by changing the dictionary after you've called it.

Python Dictionary – How to Delete All Keys Except One in a Dictionary

Why don't you just create a new one?

lang = {'en': lang['en']}

Edit: Benchmark between mine and jimifiki's solution:

$ python -m timeit "lang = {'ar':'arabic', 'ur':'urdu','en':'english'}; en_value = lang['en']; lang.clear(); lang['en'] = en_value"
1000000 loops, best of 3: 0.369 usec per loop

$ python -m timeit "lang = {'ar':'arabic', 'ur':'urdu','en':'english'}; lang = {'en': lang['en']}"
1000000 loops, best of 3: 0.319 usec per loop

Edit 2: jimifiki's pointed out in the comments that my solution keeps the original object unchanged.

Best Answer

Related Solutions

Python – How to Remove Certain Keys from a Dictionary in Python

Python Dictionary – How to Delete All Keys Except One in a Dictionary

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