Python - Dictionary of Lists
Python - Dictionary of Lists
What is a dictionary of lists in Python? A dictionary in which the value for each key is a list.
For example, the following code snippet represents a dictionary of lists.
{
'fruits': ['apple', 'banana', 'cherry'],
'colors': ['red', 'blue', 'green'],
'numbers': [1, 2, 3, 4, 5]
}
Here 'fruits'
, 'colors'
, and 'numbers'
are the keys of the dictionary and their respective values are the lists.
In this tutorial, you will learn how to create a dictionary of lists, how to access a dictionary of lists, how to update a dictionary of lists, how to traverse through a dictionary of lists, with examples.
1. Creating a dictionary of lists in Python
You can use a dictionary initializer {}
to create a dictionary of lists, as shown in the following program.
Python Program
my_dict = {
'fruits': ['apple', 'banana', 'cherry'],
'colors': ['red', 'blue', 'green'],
'numbers': [1, 2, 3, 4, 5]
}
print(my_dict)
Output
{'fruits': ['apple', 'banana', 'cherry'], 'colors': ['red', 'blue', 'green'], 'numbers': [1, 2, 3, 4, 5]}
Or, you can assign the keys in dictionary with the required lists.
Python Program
# Create an emtpy dictionary
my_dict = dict()
# Add items to dictionary
my_dict['fruits'] = ['apple', 'banana', 'cherry']
my_dict['colors'] = ['red', 'blue', 'green']
my_dict['numbers'] = [1, 2, 3, 4, 5]
print(my_dict)
Output
{'fruits': ['apple', 'banana', 'cherry'], 'colors': ['red', 'blue', 'green'], 'numbers': [1, 2, 3, 4, 5]}
2. Reading the lists from a dictionary of lists in Python
You can read the inner lists in a dictionary of lists using the key as index with the dictionary variable.
In the following program, we have a dictionary of lists in my_dict, with some initial values. We shall access the list object whose key is 'fruits' and print it to the output.
Python Program
my_dict = {
'fruits': ['apple', 'banana', 'cherry'],
'colors': ['red', 'blue', 'green'],
'numbers': [1, 2, 3, 4, 5]
}
print(my_dict['fruits'])
Output
['apple', 'banana', 'cherry']
3. Updating the lists in a dictionary of lists in Python
You can modify the lists inside the dictionary of lists, just like any other list.
In the following program, we have a dictionary of lists in my_dict, with some initial values. We shall access the list object whose key is 'fruits' and add a new item to the list.
Python Program
my_dict = {
'fruits': ['apple', 'banana', 'cherry'],
'colors': ['red', 'blue', 'green'],
'numbers': [1, 2, 3, 4, 5]
}
my_dict['fruits'].append('fig')
my_dict['fruits'].append('mango')
print(my_dict)
Output
{'fruits': ['apple', 'banana', 'cherry', 'fig', 'mango'], 'colors': ['red', 'blue', 'green'], 'numbers': [1, 2, 3, 4, 5]}
4. Traversing through a dictionary of lists in Python
You can traverse through the dictionary of lists using a For loop.
In the following program, we traverse through the dictionary of lists my_dict using a For loop.
Python Program
my_dict = {
'fruits': ['apple', 'banana', 'cherry'],
'colors': ['red', 'blue', 'green'],
'numbers': [1, 2, 3, 4, 5]
}
for key, value in my_dict.items():
print(f"{key}: {value}")
Output
fruits: ['apple', 'banana', 'cherry']
colors: ['red', 'blue', 'green']
numbers: [1, 2, 3, 4, 5]
Summary
In this tutorial, we learned what a dictionary of lists, how to create them, how to access inner lists in the dictionary using keys, and how to update the lists, how to traverse through a dictionary of lists using For loop, with help of well detailed Python programs.