Python Dictionary | pop() method

Python language specified pop() for almost all containers, be it list, set etc. This particular article focuses on illustrating the pop() method offered by Python dictionaries. This method is useful for the programmers who deal with the dictionary too often.

Syntax : dict.pop(key, def)

Parameters :
key : The key whose key-value pair has to be returned and removed.
def : The default value to return if specified key is not present.



Returns :
Value associated to deleted key-value pair, if key is present.
Default value if specified if key is not present.
KeyError, if key not present and default value not specified.

 

Code #1 : Demonstrating working of pop(), when key is present.

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# Python 3 code to demonstrate
# working of pop()
  
# initializing dictionary 
test_dict = { "Nikhil" : 7, "Akshat" : 1, "Akash" : 2 }
  
# Printing initial dict
print ("The dictionary before deletion : " + str(test_dict))
  
# using pop to return and remove key-value pair.
pop_ele = test_dict.pop('Akash')
  
# Printing the value associated to popped key 
print ("Value associated to poppped key is : " + str(pop_ele))
  
# Printing dictionary after deletion
print ("Dictionary after deletion is : " + str(test_dict))

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Output :

The dictionary before deletion : {'Nikhil': 7, 'Akshat': 1, 'Akash': 2}
Value associated to poppped key is : 2
Dictionary after deletion is : {'Nikhil': 7, 'Akshat': 1}

The behavior of pop() function is different when the key is not present in dictionary. In this case, it returns the default provided value or KeyError in case even default is not provided.

Code #2 : Demonstrating the working of pop() without key

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# Python 3 code to demonstrate
# working of pop() without key
  
# initializing dictionary 
test_dict = { "Nikhil" : 7, "Akshat" : 1, "Akash" : 2 }
  
# Printing initial dict
print ("The dictionary before deletion : " + str(test_dict))
  
# using pop to return and remove key-value pair
# provided default
pop_ele = test_dict.pop('Manjeet', 4)
  
# Printing the value associated to popped key 
# Prints 4
print ("Value associated to poppped key is : " + str(pop_ele))
  
# using pop to return and remove key-value pair
# not provided default
pop_ele = test_dict.pop('Manjeet')
  
# Printing the value associated to popped key 
# KeyError
print ("Value associated to poppped key is : " + str(pop_ele))

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Output :

The dictionary before deletion : {'Nikhil': 7, 'Akshat': 1, 'Akash': 2}
Value associated to poppped key is : 4
Traceback (most recent call last):
  File "main.py", line 20, in 
    pop_ele = test_dict.pop('Manjeet')
KeyError: 'Manjeet'



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