Comprehensive Python Dictionaries Tutorial with 52 Code Examples

Python Dictionaries: A Comprehensive Tutorial (with 52 Code Examples)

Python dictionaries are a powerful data structure that can help you improve your coding skills. Dictionaries allow you to quickly look up values that can be associated with keys. With their flexibility, you can create a simple data storage solution or a complex application.

What Are Dictionaries in Python?

Python dictionaries are unordered collections of data that are indexed using unique keys. This means that when you search for a key, the Python interpreter will look it up in the dictionary and return the associated value. A dictionary can contain any type of data including integers, strings, tuples, and even other dictionaries. The following is an example of a basic Python dictionary.

my_dict = {
    'name' : 'John', 
    'age' : 34, 
    'hobbies' : ['soccer', 'basketball', 'tennis']
}

In this example, the ‘name’, ‘age’ and ‘hobbies’ are the keys and their corresponding values are ‘John’, ‘34’, and a list of sports respectively.

Advantages of Python Dictionaries

Using a dictionary can speed up your code compared to using lists for searching for values. Dictionaries are optimized for searching which makes them much faster than lists. In addition, dictionaries are also mutable meaning that you can add new entries or remove existing ones without having to re-write your entire dictionary.

Creating Dictionaries in Python

Here are a few different ways you can create Python dictionaries:

• Using Curly Brackets with Key-Value Pairs - You can easily create a dictionary with the syntax:

  my_dict = {key1:value1, key2:value2, ...}

• Using the dict() Constructor - Using the dict() constructor you can create dictionaries by specifying key-value pairs like so:

  my_dict = dict(key1=value1, key2=value2, ...)

• Using the fromkeys() Method - If you want to create a dictionary with the same value for each key, you can use the fromkeys() method like so:

  my_dict = dict.fromkeys(['a', 'b', 'c'], 10)

• Using Comprehension - You can also create a dictionary using a comprehension expression like so:

  my_dict = {x:x**2 for x in range(1,6)}

Python Dictionary Operations

There are several operations you can perform on Python dictionaries. We will go over some of the most common operations here.

• Adding Entries - You can add new entries to a Python dictionary using the ‘update()’ method like so:

  my_dict.update({'key':'value'})

• Removing Entries - You can remove entries from a Python dictionary using the ‘pop()’ method like so:

  my_dict.pop('key')

• Retrieving Entries - You can retrieve a value from a Python dictionary using the ‘get()’ method like so:

  my_dict.get('key')

• Updating Entries - You can update a value in a Python dictionary using the ‘update()’ method like so:

  my_dict.update({'key':'new_value'})

• Iterating - You can use the ‘for’ loop to iterate through a Python dictionary like so:

  for key, value in my_dict.items():  
      print(key, value)

Examples of Working with Dictionaries in Python

Below are some examples of working with dictionaries in Python:

• 1. Adding New Key Value Pairs: To add new key value pairs to a dictionary, use the update() method like so:

  my_dict.update({'key3':'value3'})

• 2. Updating Existing Values: To update existing values, use the update() method like so:

  my_dict.update({'key':'updated_value'})

• 3. Deleting Entries: To delete entries from a dictionary, use the pop() method like so:

  my_dict.pop('key')

• 4. Retrieving Values: To retrieve a value from a dictionary, use the get() method like so:

  my_dict.get('key')

• 5. Iterating Through a Dictionary: To iterate through a dictionary, use the for loop like so:

  for key, value in my_dict.items():  
      print(key, value)

Conclusion

Dictionaries are a powerful and convenient way to store and access data in Python. With their flexibility, you can create a simple data storage solution or a complex application. We have gone over the basics of working with dictionaries, but there is much more to learn. To dive deeper into this topic, take a look at our comprehensive tutorial with 52 code examples.