Python Dictionary | setdefault() method

Dictionary in Python is an unordered collection of data values, used to store data values like a map, which unlike other Data Types that hold only single value as an element, Dictionary holds key : value pair.

In Python Dictionary, setdefault() method returns the value of a key (if the key is in dictionary). If not, it inserts key with a value to the dictionary.

Syntax: dict.setdefault(key[, default_value])



Parameters: It takes two parameters:
key – Key to be searched in the dictionary.
default_value (optional) – Key with a value default_value is inserted to the dictionary if key is not in the dictionary. If not provided, the default_value will be None.

Returns:
Value of the key if it is in the dictionary.
None if key is not in the dictionary and default_value is not specified.
default_value if key is not in the dictionary and default_value is specified.

 
Example #1:

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# Python program to show working
# of setdefault() method in Dictionary
  
# Dictionary with single item 
Dictionary1 = { 'A': 'Geeks', 'B': 'For', 'C': 'Geeks'}
  
# using setdefault() method
Third_value = Dictionary1.setdefault('C')
print("Dictionary:", Dictionary1)
print("Third_value:", Third_value)

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Output:


Dictionary: {'A': 'Geeks', 'C': 'Geeks', 'B': 'For'}
Third_value: Geeks


 

Example #2: When key is not in the dictionary.











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# Python program to show working 


# of setdefault() method in Dictionary 


  


# Dictionary with single item  


Dictionary1 = { 'A': 'Geeks', 'B': 'For'} 


  


# using setdefault() method 


# when key is not in the Dictionary 


Third_value = Dictionary1.setdefault('C') 


print("Dictionary:", Dictionary1) 


print("Third_value:", Third_value) 


  


# using setdefault() method 


# when key is not in the Dictionary 


# but default value is provided 


Fourth_value = Dictionary1.setdefault('D', 'Geeks') 


print("Dictionary:", Dictionary1) 


print("Fourth_value:", Fourth_value) 



















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Output:


Dictionary: {'A': 'Geeks', 'B': 'For', 'C': None}
Third_value: None
Dictionary: {'A': 'Geeks', 'B': 'For', 'C': None, 'D': 'Geeks'}
Fourth_value: Geeks



          
          
          
          

            

    

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