Unlocking the Power of Python Dictionaries

What are Python Dictionaries?

A Python dictionary is a data type that stores variables in an unordered way, where values are mapped to keys and can be easily accessed using each item’s key. A key is an immutable element that represents a value in a dictionary.

Properties of Python Dictionaries

Python dictionaries have several distinct behaviors that set them apart from other data structures:

• Immutable dictionary keys
• Unordered collection of data
• Multiple data types for values
• Key data types can be numbers, strings, floats, booleans, tuples, and built-in objects like classes and functions
• Dictionary keys must be unique; if duplicates are defined, Python considers the last duplicate

Declaring and Managing Dictionaries

To declare a dictionary in Python, you can wrap a sequence of value pairs (key and key-value) in curly braces, separated by commas:

my_dict = {'key1': 'value1', 'key2': 'value2'}

You can also define an empty dictionary using empty curly braces:

empty_dict = {}

Retrieving and Updating Dictionary Items

To retrieve an item in a dictionary, use the dictionary name with the item’s key in square brackets:

value = my_dict['key1']

To insert or update an item, use the assignment operator:

my_dict['new_key'] = 'new_value'

Deleting Dictionary Items

You can remove an item from a dictionary by retrieving the item using the key and then deleting it using the del() command:

del my_dict['key1']

You can also delete the entire dictionary:

del my_dict

Looping Through Dictionary Items

Looping is available in Python to perform complex dictionary operations, such as deleting all items with empty keys or retrieving data from nested dictionaries:

for key, value in my_dict.items():
    print(f"Key: {key}, Value: {value}")

Nested Dictionaries

A nested dictionary is a dictionary that contains another dictionary as a key-value:

nested_dict = {'key1': {'subkey1': 'ubvalue1', 'ubkey2': 'ubvalue2'}}

You can use nested dictionaries to associate a group of items as a whole using a specific key while associating each item with its keys.

Retrieving Items from Nested Dictionaries

To retrieve an item from a nested dictionary, you must use two or more keys to get the key-value you need, depending on the number of nests the dictionary contains:

subvalue = nested_dict['key1']['subkey1']

Python Dictionary Functions

Python functions have specific uses that help ease the work on developers. Here are some built-in Python functions you can use to perform simple operations on a dictionary:

• cmp(dict1, dict2): compares two dictionaries to find out whether they have equal values.
• len(dict): gets the length of the dictionary passed in it and returns the total number of items in a list.
• str(dict): gets the printable string representation of a dictionary passed in it.
• type(): returns the data type of a variable passed in it.

Python Dictionary Methods

Python methods, similar to functions, allow you to reuse and perform operations prebuilt for you. Here are some built-in Python methods you can use to perform operations on a dictionary:

• dict.clear(): removes all items from the dictionary to return an empty dictionary.
• dict.copy(): gets a copy of the dictionary passed to it.
• dict.fromkey(): creates a dictionary from a sequence of values.
• dict.has_key(): checks whether a key exists in the dictionary passed to it.
• dict.items(): gets a list of a dictionary’s keys and values arranged in tuple pairs.
• dict.keys(): returns a list of all existing keys in the dictionary.
• dict.update(dict2): inserts a dictionary’s item into another dictionary or updates the values where appropriate.
• dict.values(): returns a list of values existing in a dictionary without their keys.