Python, one of the most widely used programming languages in the world, offers many powerful built-in types. One of those types is the Python dictionary, or “dict” as it’s commonly known. For enthusiastic coders, whether you’re just starting out or have years of experience behind you, understanding dictionaries is an essential part of mastering Python.
Table of contents
What is a Python Dictionary?
A Python dictionary is a built-in data type that stores data in a key-value pair structure. Imagine a dictionary in the real world: you have a word (the key), and it corresponds to a definition (the value). This relation between word and definition forms a key-value pair.
Dictionaries are useful for when you want to store and retrieve data based on unique keys instead of their positions in a list. They are especially useful in situations where you need a logical association between a key and a value.
Dicts are a crucial tool for any Python programmer, simply because of their flexibility and efficiency. They are powerful, easy to use, and fast, making them instrumental in handling complex data structures. Mastering Python dicts can give you better control over your data, making your algorithms more efficient, and your code more readable.
Creating a Dictionary
Python dictionaries are created using curly braces {}. Let’s have a look at an example:
my_dict = {
'apple': 'a fruit',
'car': 'a vehicle',
'dinner': 'an evening meal'
}
print(my_dict)In this example, ‘apple’, ‘car’, and ‘dinner’ are keys, while ‘a fruit’, ‘a vehicle’, and ‘an evening meal’ are their respective values. When you print the dictionary, you get the key-value pairs.
Accessing Values in a Dictionary
You can access a dictionary’s value by calling its key inside square brackets []:
Let’s access the value for key ‘car’.
print(my_dict['car'])
This will print ‘a vehicle’, which is the value associated with the key ‘car’.
Modifying Values in a Dictionary
Dicts in python are mutable. This means you can change the value associated with a particular key in the dictionary. Here’s how:
my_dict['dinner'] = 'a meal in the evening' print(my_dict)
This will change the value of ‘dinner’ from ‘an evening meal’ to ‘a meal in the evening’.
Adding Elements to a Dictionary
You can add a new key-value pair to a python dictionary using the same syntax as modifying values. Here’s an example:
my_dict['banana'] = 'a tropical fruit' print(my_dict)
This will add a new key-value pair ‘banana’: ‘a tropical fruit’ to the dictionary.
Removing Elements from a Dictionary
You can remove elements from a Python dictionary using the del keyword. Let’s remove the key-value pair for ‘car’.
del my_dict['car'] print(my_dict)
This will remove the ‘car’: ‘a vehicle’ pair from the dictionary.
Checking If a Key Exists in a Dictionary
The ‘in’ keyword allows you to check if a certain key exists in the dictionary. This will return a boolean value.
print('banana' in my_dict)This will print True if ‘banana’ is a key in my_dict, and False otherwise.
Iterating Over a Dictionary
You can iterate over a Python dictionary using a for loop. Here’s how to print all key-value pairs in a dictionary:
for key, value in my_dict.items():
print(key, ' : ', value)This will print each key followed by its associated value.
Get All Keys and Values Separately:
You can extract all the keys and values in a dictionary separately using the keys() and values() methods.
print(my_dict.keys()) print(my_dict.values())
This will print out all the keys and values in the dictionary separately.
Where to Go Next?
Now you’ve had a taste of what Python dictionaries are capable of, the next question you might have is, “where to go next?”.
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Conclusion
Python dictionaries are a powerful and indispensable tool in any programmer’s arsenal. The efficiency and flexibility they offer in storing and manipulating data is second to none. As you continue to develop and enhance your Python skills, you’ll find yourself using them more and more. They truly embody Python’s philosophy of being ‘simple to learn and powerful to use’.
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