What is a Dictionary in Python?
In Python, a dictionary (also known as an associative array or hash) is a data structure that stores mappings of unique keys to values. Dictionaries are mutable and can be used to store any type of object.
Why Create a Dictionary in Python?
Creating a dictionary in Python allows you to efficiently store and retrieve key-value pairs, making it an essential tool for many applications, such as data analysis, web development, and more.
How to Create a Dictionary in Python
To create a dictionary in Python, you can use the built-in `dict` function or the `{}` syntax. Here’s how:
“`
my_dict = {} # empty dictionary
print(my_dict) # prints: {}
or
my_dict = dict() # same as above
print(my_dict) # prints: {}
“`
Adding Key-Value Pairs to a Dictionary
To add key-value pairs to your dictionary, you can use the assignment operator (`=`). Here’s how:
“`
my_dict[‘name’] = ‘John’
my_dict[‘age’] = 30
print(my_dict) # prints: {‘name’: ‘John’, ‘age’: 30}
“`
Accessing Values in a Dictionary
To access the values stored in your dictionary, you can use the key. Here’s how:
“`
print(my_dict[‘name’]) # prints: John
print(my_dict[‘age’]) # prints: 30
“`
Using Dictionaries with Other Data Structures
Dictionaries are often used in combination with other data structures, such as lists and sets. For example, you can use a dictionary to store the results of a database query:
“`
import sqlite3
# connect = sqlite3.connect(‘my_database.db’)
cursor = connect.cursor()
# create a table
cursor.execute(”’
CREATE TABLE IF NOT EXISTS users (
id INTEGER PRIMARY KEY,
name TEXT,
age INTEGER
);
”’)
# insert data into the table
cursor.executemany(”’
INSERT INTO users (name, age)
VALUES (?, ?);
”’, [
(‘John’, 30),
(‘Jane’, 25),
(‘Bob’, 40)
])
connect.commit()
connect.close()
# create_dict = {}
for row in cursor.fetchall():
create_dict[row[0]] = {‘name’: row[1], ‘age’: row[2]}
print(create_dict) # prints: {1: {‘name’: ‘John’, ‘age’: 30}, 2: {‘name’: ‘Jane’, 3: {‘name’: ‘Bob’, ‘age’: 40}}
“`
Conclusion
In this article, we’ve covered the basics of creating a dictionary in Python. We’ve also explored how to add key-value pairs and access values stored in your dictionary. Additionally, we’ve shown you how to use dictionaries with other data structures.
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