# CBSE Class 11 Python Dictionary Methods Comprehensive Notes with Practice Questions

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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

OUTPUT

Two
Cat
None

```

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:

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

### Python Dictionary Methods – True/False:

1. Dictionary is mutable data type.
2. Keys of dictionary must be unique.
3. pop( ) returns the deleted element.
4. length( ) function return the length of dictionary.
5. D = { } – generate an empty string.

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