Python dictionary setdefault() method

In this tutorial, we are going to learn setdefault() method in Python with some easy examples. That is most important to many programmers while dealing with a dictionary.

Usually, in Python, while dealing with the “Dictionary” datatype sometimes we require to find whether an element is present in a dictionary or not.

To solve this problem we use a method in Python called “setdefault()” method.

Python setdefault() method

Before starting, first of all, let us know about a dictionary in Python.

Dictionary in Python: A dictionary is a collection datatype that contains elements, usually stored in the form of keys and values. The elements in a dictionary are unordered, unchangeable and indexed.

Representation:

We usually represent a dictionary in Python by using “{}” brackets.

Note:

In the dictionary, values are stored in “key: value” pairs.

setdefault() method:

Syntax:

setdefault(key,value)

Parameters:

key: The element that we want to search in the dictionary.

value: The value that is to be inserted in the dictionary if the key is not found.

Note:

When the value is not specified then by default it assigns to “None”.

Calling:

Because setdefault() is a method, therefore, we use the dot operator “.” to call the setdefault() method.

Return:

The setdefault() method returns THE VALUE OF THE KEY IF IT IS PRESENT IN THE DICTIONARY, else it INSERTS KEY WITH THE SPECIFIED VALUE INTO THE DICTIONARY.

EXAMPLE 1:

#Python code to demonstrate setdefault() method

>>> dict = {"a" : "code","b" : "speedy","c" : "software","d" : "solutions"}

>>> print(dict)

>>> dict.setdefault("c")

OUTPUT:

{'a': 'code', 'b': 'speedy', 'c': 'software', 'd': 'solutions'}

'software'

In the above example by calling the setdefault() method we get the value of key i.e ‘software’.

EXAMPLE 2:

#Python code to demonstrate setdefault() method
>>> dict = {"a" : "code","b" : "speedy","c" : "software","d" : "solutions"}

>>> print(dict)

>>> dict.setdefault("e")

>>> print(dict)

OUTPUT:

{'a': 'code', 'b': 'speedy', 'c': 'software', 'd': 'solutions'}

{'a': 'code', 'b': 'speedy', 'c': 'software', 'd': 'solutions', 'e': None}

In the above example, because the key is not present in the dictionary therefore setdefault() method returns “none”.

EXAMPLE 3:

#Python code to demonstrate setdefault() method

>>> dict = {"a" : "code","b" : "speedy","c" : "software","d" : "solutions"}

>>>print(dict)

>>> dict.setdefault("f","company")

>>> print(dict)

OUTPUT:

{'a': 'code', 'b': 'speedy', 'c': 'software', 'd': 'solutions'}

{'a': 'code', 'b': 'speedy', 'c': 'software', 'd': 'solutions', 'e': None, 'f': 'company'}
In the above example because the key "f" isn't present in the dictionary setdefault() method, therefore, inserts the value "company" into the dictionary.

Finally, I hope that this tutorial was helpful to understand the setdefault() method successfully!!

Also read:

• Python Class and Instance Attributes
• Python rindex() method