Dictionary Methods

Dictionary uses several built-in methods for manipulation. They are listed below:

i. update()

The update() method updates the value of the key provided to it if the item already exists in the dictionary, else it creates a new key-value pair.

Example:

info = {'name':'Karan', 'age':19, 'eligible':True}
print(info)
info.update({'age':20})
info.update({'DOB':2001})
print(info)

Output:

{'name': 'Karan', 'age': 19, 'eligible': True}
{'name': 'Karan', 'age': 20, 'eligible': True, 'DOB': 2001}

Removing items from dictionary:

There are a few methods that we can use to remove items from dictionary.

ii. clear():

The clear() method removes all the items from the list.

Example:

info = {'name':'Karan', 'age':19, 'eligible':True}
info.clear()
print(info)

Output:

{}

iii. pop():

The pop() method removes the key-value pair whose key is passed as a parameter.

Example:

info = {'name':'Karan', 'age':19, 'eligible':True}
info.pop('eligible')
print(info)

Output:

{'name': 'Karan', 'age': 19}

iv. popitem():

The popitem() method removes the last key-value pair from the dictionary.

Example:

info = {'name':'Karan', 'age':19, 'eligible':True, 'DOB':2003}
info.popitem()
print(info)

Output:

{'name': 'Karan', 'age': 19, 'eligible': True}

v. del:

we can also use the del keyword to remove a dictionary item.

Example:

info = {'name':'Karan', 'age':19, 'eligible':True, 'DOB':2003}
del info['age']
print(info)

Output:

{'name': 'Karan', 'eligible': True, 'DOB': 2003}

If key is not provided, then the del keyword will delete the dictionary entirely.

Example:

info = {'name':'Karan', 'age':19, 'eligible':True, 'DOB':2003}
del info
print(info)

Output:

NameError: name 'info' is not defined

Practice

ep1 = {122: 45, 123: 89, 567: 69, 670: 69}
ep2 = {222: 67, 566: 90}

# ep1.update(ep2)
# ep1.clear()
# ep1.pop(122)
ep1.popitem()
del ep1[122]
print(ep1) 

Output:

{123: 89, 567: 69}

Explanation

• ep1 = {122: 45, 123: 89, 567: 69, 670: 69}

  • Creates a dictionary with employee IDs as keys and values as data.

• ep2 = {222: 67, 566: 90}

  • Another dictionary (not used in final operations because update() is commented out).

• ep1.update(ep2) (commented)

  • Would add all key-value pairs from ep2 into ep1.

• ep1.clear() (commented)

  • Would remove all elements from ep1.

• ep1.pop(122) (commented)

  • Would remove key 122 and return its value (45).

• ep1.popitem()

  • Removes the last inserted key-value pair from the dictionary.

  • After this, one item is deleted from ep1.

• del ep1[122]

  • Deletes the key 122 and its value from the dictionary.

  • ⚠️ Important: This will only work if key 122 still exists after popitem().

• print(ep1)

  • Displays the final dictionary after deletions.