dictionary in python

In Python, a dictionary is a built-in data structure that stores data in key-value pairs. Dictionaries are mutable, meaning they can be changed after they are created, and they are unordered, meaning the order in which the key-value pairs are stored is not guaranteed.

Key Features of a Dictionary:

• Keys and Values: Each item in a dictionary consists of a key and its corresponding value. Keys must be unique and immutable (e.g., strings, numbers, or tuples), while values can be of any data type and can be repeated.
• Syntax: Dictionaries are defined using curly braces {}, with key-value pairs separated by colons : and each pair separated by commas.

Example of a Dictionary:

# Creating a dictionary
my_dict = {
    'name': 'Alice',
    'age': 25,
    'city': 'New York'
}

# Accessing a value using its key
print(my_dict['name'])  # Output: Alice

# Adding a new key-value pair
my_dict['profession'] = 'Engineer'

# Updating a value
my_dict['age'] = 26

# Deleting a key-value pair
del my_dict['city']

# Checking if a key exists
if 'name' in my_dict:
    print('Name is present in the dictionary')

# Iterating over keys and values
for key, value in my_dict.items():
    print(f'{key}: {value}')

Key Operations:

• Accessing values: Use the key inside square brackets ([]) to access the value associated with that key.
• Adding or updating values: Assign a value to a key. If the key already exists, its value will be updated; otherwise, a new key-value pair is added.
• Deleting key-value pairs: Use the del statement or the pop() method to remove a key-value pair.
• Iteration: Use methods like .keys(), .values(), and .items() to iterate over keys, values, or both.

Dictionaries are extremely useful for scenarios where you need to associate a unique key with a value and perform efficient lookups.