Introduction
Python dictionaries are powerful data structures for storing key-value pairs. Below is a quick reference to the most commonly used dictionary methods with brief examples.
1. clear()
Removes all items from the dictionary.
d = {'a': 1, 'b': 2}
d.clear() # {}
2. copy()
Returns a shallow copy of the dictionary.
d = {'a': 1, 'b': 2}
new_d = d.copy() # {'a': 1, 'b': 2}
3. fromkeys(iterable, value)
Creates a new dictionary from keys and an optional value.
keys = ['a', 'b', 'c']
d = dict.fromkeys(keys, 0) # {'a': 0, 'b': 0, 'c': 0}
4. get(key, default)
Returns the value of a key if it exists, otherwise returns the default value.
d = {'a': 1, 'b': 2}
d.get('a') # 1
d.get('c', 0) # 0
5. items()
Returns a view object that displays a list of a dictionary's key-value pairs.
d = {'a': 1, 'b': 2}
d.items() # dict_items([('a', 1), ('b', 2)])
6. keys()
Returns a view object that displays a list of all the keys in the dictionary.
d = {'a': 1, 'b': 2}
d.keys() # dict_keys(['a', 'b'])
7. pop(key, default)
Removes and returns the value for the specified key. If the key is not found, the default value is returned.
d = {'a': 1, 'b': 2}
d.pop('a') # 1, d = {'b': 2}
d.pop('c', 0) # 0
8. popitem()
Removes and returns the last inserted key-value pair as a tuple.
d = {'a': 1, 'b': 2}
d.popitem() # ('b', 2)
9. setdefault(key, default)
Returns the value of a key if it exists, otherwise inserts the key with a default value.
d = {'a': 1}
d.setdefault('b', 2) # 2, d = {'a': 1, 'b': 2}
10. update([other])
Updates the dictionary with elements from another dictionary or iterable of key-value pairs.
d = {'a': 1, 'b': 2}
d.update({'b': 3, 'c': 4}) # {'a': 1, 'b': 3, 'c': 4}
11. values()
Returns a view object that displays a list of all the values in the dictionary.
d = {'a': 1, 'b': 2}
d.values() # dict_values([1, 2])
12. len(dict)
Returns the number of key-value pairs in a dictionary.
d = {'a': 1, 'b': 2}
len(d) # 2
13. in
Checks if a key exists in a dictionary.
d = {'a': 1, 'b': 2}
'a' in d # True
'c' in d # False
14. del
Deletes a key-value pair from the dictionary.
d = {'a': 1, 'b': 2}
del d['a'] # d = {'b': 2}
Conclusion
Python dictionaries provide a wide range of methods for key-value management. Whether retrieving, updating, or deleting data, these methods offer efficient ways to manipulate dictionaries in Python.
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