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Python Dictionary Methods:

There are many methods of dictionary in python. Let’s do some of the important function with example.

len( ) :

This function returns the length of Dictionary means, it returns the total number of Key-Value pairs present in the dictionary. for example:

A = {1 : "One", 2 : "Two", 3 : "Three"}
B = {'A' : "Apple", 'B' : "Bat", 'C' : "Cat", 'D' : "Doll"}
print("Length of dictionary A is :", len(A))
print("Length of dictionary B is :", len(B))

OUTPUT

Length of dictionary A is : 3
Length of dictionary B is : 4

clear( ) :

This function simply removes all items from the dictionary. for example

A = {1 : "One", 2 : "Two", 3 : "Three"}
B = {'A' : "Apple", 'B' : "Bat", 'C' : "Cat", 'D' : "Doll"}
A.clear()
print("Length of dictionary A is :", len(A))
print("Length of dictionary B is :", len(B))

OUTPUT

Length of dictionary A is : 0
Length of dictionary B is : 4

NOTE : This function only remove element/items from the dictionary. It does not delete the dictionary

get( ):

This function simply return the value of the required Key. for example

A = {1 : "One", 2 : "Two", 3 : "Three"}
B = {'A' : "Apple", 'B' : "Bat", 'C' : "Cat", 'D' : "Doll"}
print(A.get(2))
print(B.get('C'))
print(A.get(4)) #This key is not available in dictionary A so return NONE
print(A.get(4),"Key Not Found") #We can specify our message to display if key not found


OUTPUT

Two
Cat
None
Key Not Found

NOTE: If key is not available in dictionary then this method will return None or customized message as shown above

items( ):

This function returns all the key value pair of dictionary in the form of list of tuples. for example

A = {1 : "One", 2 : "Two", 3 : "Three"}
B = {'A' : "Apple", 'B' : "Bat", 'C' : "Cat", 'D' : "Doll"}
print(A.items())
print(B.items())

OUTPUT

dict_items([(1, 'One'), (2, 'Two'), (3, 'Three')])
dict_items([('A', 'Apple'), ('B', 'Bat'), ('C', 'Cat'), ('D', 'Doll')])

Q1. What is the difference between print(A) and print(A.items( )) Where ‘A’ is dictionary given above.

Ans. There is difference in the output of dictionary as print command print all key-value pair in curly braces while itrms( ) return all key value pairs as a list of tuples. for example

A = {1 : "One", 2 : "Two", 3 : "Three"}
print(A.items())
print(A)

OUTPUT:

dict_items([(1, 'One'), (2, 'Two'), (3, 'Three')])
{1: 'One', 2: 'Two', 3: 'Three'}

keys( ):

This function return all the keys of dictionary in the form of List. for example :

A = {1 : "One", 2 : "Two", 3 : "Three"}
B = {'A' : "Apple", 'B' : "Bat", 'C' : "Cat", 'D' : "Doll"}
print(A.keys())
print(B.keys())

OUTPUT:

dict_keys([1, 2, 3])
dict_keys(['A', 'B', 'C', 'D'])

values( ):

This function return all the values of dictionary in the form of List. for example :

A = {1 : "One", 2 : "Two", 3 : "Three"}
B = {'A' : "Apple", 'B' : "Bat", 'C' : "Cat", 'D' : "Doll"}
print(A.values())
print(B.values())

OUTPUT:

dict_values(['One', 'Two', 'Three'])
dict_values(['Apple', 'Bat', 'Cat', 'Doll'])

update( ):

This function merge the key value air of two dictionary into one. In simple words it simply join/merge the two dictionary. It merge the keys and values of one dictionary into other and overwrites the values of the same key. for example:

A = {1 : "One", 2 : "Two", 3 : "Three"}
B = {1: 'Amit', 2: 'Sunil', 5: 'Lata', 6: 'Suman', 7: 'Ravi'}
A.update(B)
print(A)

OUTPUT

{1: 'Amit', 2: 'Sunil', 3: 'Three', 5: 'Lata', 6: 'Suman', 7: 'Ravi'}

#It over writes the values of same keys and add the values of different keys

pop( ):

This function not only delete the element of required key but also return the deleted value.

B = {1: 'Amit', 2: 'Sunil', 5: 'Lata', 6: 'Suman', 7: 'Ravi'}
a=B.pop(2) #It returns the element of Key - 2
print(a)
print(B)

OUTPUT

Sunil
{1: 'Amit', 5: 'Lata', 6: 'Suman', 7: 'Ravi'}
______________________________________________________________________________________________________________

B = {1: 'Amit', 2: 'Sunil', 5: 'Lata', 6: 'Suman', 7: 'Ravi'}
a=B.pop(6) #It returns the element of Key - 6
print(a)
print(B)

OUTPUT

Suman
{1: 'Amit', 2: 'Sunil', 5: 'Lata', 7: 'Ravi'}

Assignment:

Python Dictionary Methods – Fill in the blanks:

All the elements of dictionary are enclosed in ______________ bracket.
Key and it’s value are separated by symbol ___________________ in dictionary.
Dictionary is _________ data type(mapping/sequence).
_________________ methods create an empty dictionary.
__________ method delete all the elements of dictionary.