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:
Python3
# 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) |
Output:
Dictionary: {'A': 'Geeks', 'C': 'Geeks', 'B': 'For'} Third_value: Geeks
Example #2: When key is not in the dictionary.
Python3
# 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) |
Output:
Dictionary: {'A': 'Geeks', 'B': 'For', 'C': None} Third_value: None Dictionary: {'A': 'Geeks', 'B': 'For', 'C': None, 'D': 'Geeks'} Fourth_value: Geeks