Python

pop() method in dictionary

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pop() method in dictionary - Python

This method is used to remove an item from a dictionary based on the specified key.

It will throw an error KeyError if the specified key is not present in the dictionary and no default value is given.

It returns the value of the key that is removed from the dictionary.

The time complexity of this method is O(1) constant.

When we call the pop() method with a dictionary and pass a key as an argument, Python first calculates the hash value of the specified key and checks whether the specified index is pointing to the desired key-value pair in the hash table or not. If the key exists, Python removes the key-value pair from the hash table and returns the value associated with the removed key. If the key does not exist, a KeyError is raised to indicate that the specified key is not present in the dictionary.

Syntax –

dictionary.pop(key, default)

Parameters –

key → key of the item that you want to remove from the dictionary.

default(optional)→ default value that you want to return if the specified key is not found.

return → returns the value of the specified key if the key is found.

Example –

				
					my_dict={'a':5,'b':10,'c':15,'d':20,'e':25}
print("Original Dictionary:\n",my_dict)

my_dict.pop('d')
print("Original dictionary after removing 'd':20 from dictionary:\n",my_dict)

# Output -
# Original Dictionary:
#  {'a': 5, 'b': 10, 'c': 15, 'd': 20, 'e': 25}
# Original dictionary after removing 'd':20 from dictionary:
#  {'a': 5, 'b': 10, 'c': 15, 'e': 25}

In the above example, first we create a dictionary with some items and store it in my_dict variable.

After creating a dictionary print the dictionary on the output screen.

Then pop item(’d’:20) from the original dictionary using the .pop() method.

Finally, print the modified original dictionary on the output screen.

Example –

				
					student={'name':'anurag','year':4,'rollno':1234,'branch':'cse'}
print("Original Dictionary:",student)

return_value=student.pop('year')
print('Original Modified dictionary:",student)
print('year of the student:',return_value)

# Output -

# Original Dictionary: {'name': 'anurag', 'year': 4, 'rollno': 1234, 'branch': 'cse'}
# Original Modified dictionary: {'name': 'anurag', 'rollno': 1234, 'branch': 'cse'}
# year of the student: 4

Example – pop with the default value

				
					course={1:'Data Science',2:'Full Stack',3:'Devops',4:'Cyber Security'}
print("Available Courses:\n",course)

return_course=course.pop(5,'course not found')
print("Modified Courses:\n",course)
print("return value:",return_course)

# Output -
# Available Courses: 
# {1: 'Data Science', 2: 'Full Stack', 3: 'Devops', 4: 'Cyber Security'}
# Modified Courses: 
# {1: 'Data Science', 2: 'Full Stack', 3: 'Devops', 4: 'Cyber Security'}
# return value: course not found

Example – pop without a default value and the item is not present

				
					vacancy={'HR':1,'developer':3,'content writer':2,'data analyst':4}
print("Vacancy Available:\n",vacancy)

vacancy.pop('project manager')

# Output -
# Vacancy Available:
# {'HR': 1, 'developer': 3, 'content writer': 2, 'data analyst': 4}
# Traceback (most recent call last):
  # File "/home/main.py", line 4, in <module>
    # vacancy.pop('project manager')
# KeyError: 'project manager'

Python

pop() method in dictionary

pop() method in dictionary - Python

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