A Python dictionary is a built-in data structure that stores a collection of key-value pairs. It is also known as an associative array or hash table in other programming languages. Dictionaries are unordered, meaning the elements are not stored in a specific order, and they are mutable, allowing you to add, modify, and remove items.
Here’s an example of a Python dictionary:
person = { "name": "John", "age": 30, "city": "New York" } In this example, "name", "age", and "city" are the keys, and "John", 30, and "New York" are the corresponding values. You can access the values by providing the key in square brackets:
print(person["name"]) # Output: JohnYou can also modify the values associated with keys or add new key-value pairs:
person["age"] = 31 # Modifying the value person["occupation"] = "Engineer" # Adding a new key-value pair print(person) # Output: {'name': 'John', 'age': 31, 'city': 'New York', 'occupation': 'Engineer'} To check if a key exists in the dictionary, you can use the in operator:
if "name" in person: print("Name exists in the dictionary.") You can iterate over the keys or values of a dictionary using loops or perform operations like getting the number of items in the dictionary using the len() function.
for key in person: print(key, person[key]) # Output: name John, age 31, city New York, occupation Engineer print(len(person)) # Output: 4 Python dictionaries are versatile data structures that are widely used for mapping and storing data based on keys for efficient retrieval.