Introduction to Python Dictionaries
Python Dictionaries
A dictionary is an unordered collection of key-value pairs.
It is also known as an associative array or hash table. Dictionaries are defined by enclosing the key-value pairs in curly braces {}
or by using the dict()
constructor.
Each key in a dictionary must be unique, and it is used to access its corresponding value.
Here's an example of a dictionary in Python:
person = {
"name": "John",
"age": 30,
"city": "New York"
}
Accessing Dictionary Values
You can access the value associated with a key in a dictionary by using the key inside square brackets []
.
person = {
"name": "John",
"age": 30,
"city": "New York"
}
print(person["name"]) # Output: John
print(person["age"]) # Output: 30
Adding and Modifying Dictionary Elements
You can add a new key-value pair to a dictionary by assigning a value to a new or existing key.
person = {
"name": "John",
"age": 30,
"city": "New York"
}
person["occupation"] = "Engineer" # Add a new key-value pair
person["age"] = 31 # Modify the value of an existing key
print(person) # Output: {'name': 'John', 'age': 31, 'city': 'New York', 'occupation': 'Engineer'}
Dictionary Methods
Dictionaries have several built-in methods that you can use, such as keys()
, values()
, items()
, get()
, pop()
, popitem()
, clear()
, update()
, and more.
person = {
"name": "John",
"age": 30,
"city": "New York"
}
print(person.keys()) # Output: dict_keys(['name', 'age', 'city'])
print(person.values()) # Output: dict_values(['John', 30, 'New York'])
print(person.items()) # Output: dict_items([('name', 'John'), ('age', 30), ('city', 'New York')])
print(person.get("name")) # Output: John
print(person.pop("age")) # Output: 30
print(person) # Output: {'name': 'John', 'city': 'New York'}
person.clear() # Remove all elements from the dictionary
print(person) # Output: {}
Checking Dictionary Membership
You can check if a key exists in a dictionary using the in
operator. It returns True
if the key is found in the dictionary and False
otherwise.
person = {
"name": "John",
"age": 30,
"city": "New York"
}
print("name" in person) # Output: True
print("occupation" in person) # Output: False