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Dictionaries in Python
A dictionary in Python is a collection of key-value pairs. Here are some common methods used with dictionaries:
1. clear()
Removes all items from the dictionary.
# Clear the dictionary
my_dict.clear()
print(my_dict) # Output: {}
2. copy()
Returns a shallow copy of the dictionary.
# Create a shallow copy of the dictionary
new_dict = my_dict.copy()
3. fromkeys()
Returns a new dictionary with the specified keys and the same value for each key.
# Create a dictionary with specified keys and default value
keys = ['a', 'b', 'c']
default_value = 'default'
new_dict = dict.fromkeys(keys, default_value)
print(new_dict) # Output: {'a': 'default', 'b': 'default', 'c': 'default'}
4. get()
Returns the value for the specified key. Returns None if the key is not found.
# Get the value for a key
value = my_dict.get('key')
print(value) # Output: None (if 'key' is not found)
5. items()
Returns a view object that displays a list of key-value tuple pairs.
# Get a view object of key-value pairs
items = my_dict.items()
print(items) # Output: dict_items([('key1', 'value1'), ('key2', 'value2'), ...])
6. keys()
Returns a view object that displays a list of all the keys in the dictionary.
# Get a view object of keys
keys = my_dict.keys()
print(keys) # Output: dict_keys(['key1', 'key2', ...])
7. pop()
Removes the element with the specified key and returns its value. Raises a KeyError if the key is not found.
# Remove and return the value for a key
value = my_dict.pop('key')
print(value) # Output: 'value' (if 'key' is found)
8. popitem()
Removes and returns an arbitrary key-value pair as a tuple. Raises a KeyError if the dictionary is empty.
# Remove and return an arbitrary key-value pair
key, value = my_dict.popitem()
print(key, value) # Output: ('key', 'value')
9. setdefault()
Returns the value of the specified key. If the key does not exist, inserts the key with the specified value.
# Get the value for a key; if key does not exist, insert key with specified value
value = my_dict.setdefault('key', 'default_value')
print(value) # Output: 'value' (if 'key' exists), 'default_value' (if 'key' does not exist)
10. update()
Updates the dictionary with the specified key-value pairs.
# Update the dictionary with key-value pairs from another dictionary
other_dict = {'key1': 'new_value1', 'key2': 'new_value2'}
my_dict.update(other_dict)
print(my_dict)
11. values()
Returns a view object that displays a list of all the values in the dictionary.
# Get a view object of values
values = my_dict.values()
print(values) # Output: dict_values(['value1', 'value2
'])