Dictionaries

Dictionaries in Python are a type of data structure that store data in the form of key-value pairs. Each key-value pair is also known as an item. Dictionaries are useful for storing and retrieving data when the data can be referenced by a unique key.

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Creating a Dictionary:

To create a dictionary, you can use curly braces ({}) or the built-in dict() function. Each item in the dictionary is separated by a comma, with the key and value separated by a colon (:).

Example:

# Using curly braces
my_dict = {'name': 'John', 'age': 25, 'city': 'New York'}

# Using dict() function
my_dict = dict(name='John', age=25, city='New York')

Accessing Values in a Dictionary:

To access a value in a dictionary, you can use the square bracket notation with the key of the item you want to access.

Example:

my_dict = {'name': 'John', 'age': 25, 'city': 'New York'}
print(my_dict['name']) # Output: John
print(my_dict['age']) # Output: 25
print(my_dict['city']) # Output: New York

If the key you are trying to access is not present in the dictionary, a KeyError will be raised. To avoid this, you can use the get() method, which returns None if the key is not present.

Example:

my_dict = {'name': 'John', 'age': 25, 'city': 'New York'}
print(my_dict.get('name')) # Output: John
print(my_dict.get('salary')) # Output: None

Modifying a Dictionary:

To modify a value in a dictionary, you can use the square bracket notation with the key of the item you want to modify and then assign a new value to it.

Example:

my_dict = {'name': 'John', 'age': 25, 'city': 'New York'}
my_dict['age'] = 26
print(my_dict) # Output: {'name': 'John', 'age': 26, 'city': 'New York'}

To add a new key-value pair to the dictionary, you can use the square bracket notation with the new key and then assign a new value to it.

Example:

my_dict = {'name': 'John', 'age': 25, 'city': 'New York'}
my_dict['salary'] = 50000
print(my_dict) # Output: {'name': 'John', 'age': 25, 'city': 'New York', 'salary': 50000}

To delete an item from a dictionary, you can use the del keyword followed by the key of the item you want to delete.

Example:

my_dict = {'name': 'John', 'age': 25, 'city': 'New York'}
del my_dict['age']
print(my_dict) # Output: {'name': 'John', 'city': 'New York'}

You can also use the pop() method to remove an item from the dictionary and return its value.

Example:

my_dict = {'name': 'John', 'age': 25, 'city': 'New York'}
age = my_dict.pop('age')
print(age) # Output: 25
print(my_dict) # Output: {'name': 'John', 'city': 'New York'}

That’s the basics of dictionaries in Python. They are a powerful and flexible data structure that can be used in many different ways to store and retrieve data.

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