Mapping is a fundamental concept in Python programming. It allows you to store and organize data in a way that can be easily accessed and manipulated. In Python, mapping is achieved using a built-in data type called a dictionary.
What is a dictionary?
A dictionary is an unordered collection of key-value pairs, where each key is unique. It provides a way to map keys to values, allowing you to retrieve the value associated with a given key efficiently.
To create a dictionary in Python, you use curly braces {} and separate each key-value pair with a colon (:). Let’s take an example:
<code>
my_dict = {'name': 'John', 'age': 25, 'city': 'New York'}
</code>
In this example, the keys are ‘name’, ‘age’, and ‘city’, and their corresponding values are ‘John’, 25, and ‘New York’.
Accessing Values in a Dictionary
You can access the values in a dictionary by referring to its key within square brackets []. For example:
<code> print(my_dict['name']) </code>
This will output: John
Modifying Values in a Dictionary
Dictionaries are mutable, meaning you can modify their values after they have been created. To update the value associated with a specific key, simply assign the new value to that key:
<code> my_dict['age'] = 26 </code>
Now, if you print the value associated with the ‘age’ key, it will be 26.
Adding and Removing Key-Value Pairs
To add a new key-value pair to an existing dictionary, you can simply assign a value to a new key:
<code> my_dict['occupation'] = 'Software Engineer' </code>
If you print the dictionary now, it will include the new key-value pair: ‘occupation’: ‘Software Engineer’.
To remove a key-value pair from a dictionary, you can use the del statement:
<code> del my_dict['city'] </code>
This will remove the key-value pair with the key ‘city’ from the dictionary.
Iterating Over a Dictionary
You can iterate over a dictionary using a for loop. By default, iterating over a dictionary will give you its keys. However, if you want to iterate over both keys and values, you can use the .items() method:
<code>
for key, value in my_dict.items():
print(key, value)
</code>
This will output each key-value pair on separate lines.
In conclusion,
- A dictionary is Python’s built-in mapping data type.
- It allows you to store and retrieve values using unique keys.
- Dictionaries are mutable, meaning you can modify their values.
- You can add and remove key-value pairs as needed.
- Iterating over a dictionary gives you access to its keys or both keys and values.
Dictionaries are incredibly versatile and widely used in Python programming. They provide a powerful way to organize and manipulate data efficiently.
Understanding how to use dictionaries effectively will greatly enhance your Python programming skills. So go ahead, start experimenting with dictionaries in your own code!