mutation

`dict.pop`

Removes the specified key and returns its value. If the key is missing, returns default if provided; otherwise raises KeyError.

Syntax

d.pop(key[, default])

Parameters

Parameter	Purpose
key	Key to remove from the dictionary
default	Value returned when key is missing (suppresses KeyError)

Examples

>>> d = {'a': 1, 'b': 2}
>>> d.pop('a')
1
>>> d
{'b': 2}

Removes and returns the value

>>> d = {'a': 1}
>>> d.pop('missing')
Traceback (most recent call last):
  ...
KeyError: 'missing'

Without a default, missing key raises KeyError

>>> d = {'a': 1}
>>> d.pop('missing', None)
>>> d.pop('missing', 0)
0

Supply a default (even None) to make pop non-raising

>>> config = {'debug': True, 'port': 8080}
>>> debug = config.pop('debug', False)
>>> debug, config
(True, {'port': 8080})

Extract-and-remove pattern for config parsing

Gotcha

Without a default, pop raises KeyError on missing keys — pass a default (even None) to make it safe. Unlike list.pop, dict.pop requires a key argument.

Related methods

dict.popitem

Removes and returns the last inserted (key, value) pair as a 2-tuple in LIFO order. Raises KeyError if the dictionary is empty.

dict.get

Returns the value for key if key is in the dictionary, else default. If default is not given, it defaults to None so this method never raises a KeyError.

dict.clear

Removes all items from the dictionary in place, leaving it empty. Returns None.

dict.update

Updates the dictionary in place with key/value pairs from other, overwriting existing keys. Accepts another mapping, an iterable of key/value pairs, and/or keyword arguments; returns None.

dict[key] = value

Assigns value to key using bracket subscription syntax, invoking __setitem__ under the hood. Creates the entry if key is absent, or overwrites the existing value; preserves the original insertion order when the key already exists.

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