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Dictionaries in Python

 

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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
'])
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