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Getting started with Python Dictionary



Dictionary is an important data type built into Python. It contains key-value pair elements. You should know that keys are unique and that they can be only an immutable data type, a key can be for example a string, a number or a tuple, but, it can't be a list. Whereas, the values in a dictionary can be of any type.

In this article, we will see together how to create a dictionary, access values, update and delete items and some useful methods and techniques for a dictionary in Python.


1) Creating a dictionary


The dictionary can be empty. We initialize an empty dictionary using {} or dict():


There are several methods to create non-empty dictionaries in Python. We can create a dictionary using a comma-separated list of key:value pairs inside the braces. We can also create it from sequences of key-value pairs using dict() constructor. The third method consists on specifying pairs using keyword arguments in case the keys are simple strings. And finally, we can create a dictionary using key-value pairs expressions.


2) Accessing items


We can access values in a dictionary using indexing or the get() method as shown in the code below:

3) Updating items


We can update the value of a dictionary using dictionary[key]=value. If the key already exists in the dictionary the value will be updated and if the key doesn’t exist then that key-value pair will be added to the dictionary. Another method allows us to update our dictionary which is update().


4) Deleting


Several methods are used for deletion. The first one is popitem() which removes and returns the last item inserted in the dictionary. pop() method removes and return a value from a dictionary for a given key. And clear() method is used to delete all the items.

5) Some useful methods and techniques


The code below shows how to use dict.keys(), dict.values() and dict.items():



The objects returned by dict.keys(), dict.values() and dict.items() are view objects. They provide a dynamic view on the dictionary’s entries, which means that when the dictionary changes, the view reflects these changes.[Python docs]


Now, you learnt the basics of dictionaries in Python. Enjoy using this important data type.

You can find the notebook containing the source code used in this post here.


 

References:

https://www.tutorialspoint.com/python/python_dictionary.html



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